| Name | CR | Type | Environment |
| Sabosan | 5 | monstrous humanoid | warm forests or underground |
| Sagari | 1/2 | aberration | any forests |
| Saguaroi | 5 | plant | warm deserts |
| Sahkil, Esipil | 2 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Ichkoh | 7 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Kimenhul | 20 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Nucol | 4 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Pakalchi | 9 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Qolok | 16 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Wihsaak | 6 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Ximtal | 17 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahkil, Zohanil | 10 | outsider (evil, extraplanar, sahkil) | any (Ethereal Plane) |
| Sahuagin | 2 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin Mutant, Four-Armed Mutant | 3 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin Mutant, Malenti | 2 | monstrous humanoid (aquatic) | temperate or warm oceans |
| Sahuagin, Sahuagin Baron | 9 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Brute | 3 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Champion | 10 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Deep Racer | 4 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin High Priestess | 9 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Infiltrator | 7 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Lieutenant | 5 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Prince | 13 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Scout | 3 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Shark Sentry | 6 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Sahuagin, Sahuagin Underpriestess | 5 | monstrous humanoid (aquatic) | temperate or warm ocean |
| Salamander | 6 | outsider (extraplanar, fire) | any (Plane of Fire) |
| Samsaran | 1/2 | humanoid (samsaran) | any land |
| Samsaran, Reborn Samsaran | 1/2 | humanoid (samsaran) | any land |
| Sandman | 3 | outsider (earth, elemental, extraplanar) | any land (Plane of Earth) |
| Sangoi | 7 | fey | any cold or temperate land |
| Sapphire Ooze | 2 | ooze (extraplanar, shapechanger) | any (Elysium) |
| Sarcovalt | 4 | outsider (evil, extraplanar) | any (Abaddon) |
| Sard | 19 | plant | any forests |
| Sargassum Fiend | 9 | plant (aquatic) | any oceans |
| Sasquatch | 2 | humanoid (sasquatch) | temperate or cold forests |
| Satyr | 4 | fey | temperate forests |
| Satyr, Blackwood Satyr | 7 | fey
| — |
| Saumen Kar | 10 | monstrous humanoid | cold plains, hills, or desert |
| Saurian | 16 | monstrous humanoid | warm mountains |
| Sawdust Slough | 4 | plant | temperate forest |
| Saxra | 18 | undead (air) | any mountains |
| Sayona | 12 | undead | any land or underground |
| Scarab Swarm | 3 | vermin (swarm) | warm deserts |
| Scarecrow | 4 | construct | any land |
| Scarlet Walker | 12 | outsider (evil, extraplanar, lawful)
| any
|
| Sceaduinar | 7 | outsider (extraplanar) | any (Negative Energy Plane) |
| Sceazir | 9 | outsider (extraplanar) | any (Negative Energy Plane) |
| Scitalis | 12 | dragon | any land |
| Scorpion, Black Scorpion | 15 | vermin | warm deserts |
| Scorpion, Cave Scorpion | 1 | vermin | any underground |
| Scorpion, Deadfall Scorpion | 8 | vermin | temperate forests |
| Scorpion, Ghost Scorpion | 1/2 | vermin | warm deserts or underground |
| Scorpion, Giant Emperor Scorpion | 11 | vermin | warm deserts |
| Scorpion, Giant Scorpion | 3 | vermin | warm or temperate deserts, forests, plains, or underground |
| Scorpion, Greensting Scorpion | 1/4 | vermin | warm or temperate forests |
| Scrapshell | 6 | vermin (aquatic) | warm oceans |
| Scrivenite | 4 | outsider (extraplanar, lawful) | any (Axis) |
| Scylla | 16 | aberration (aquatic) | any water |
| Scythe Glass Swarm | 9 | construct (swarm) | any urban |
| Sea Bonze | 15 | undead (aquatic) | any oceans |
| Sea Cat | 4 | magical beast | warm coastlines |
| Sea Crawler | 1 | animal | temperate coasts |
| Sea Scourge | 6 | ooze (aquatic) | warm oceans |
| Sea Serpent | 12 | magical beast (aquatic) | any ocean |
| Sea Snake | 1 | animal | any oceans |
| Sea Snake, Giant Sea Snake | 7 | animal | warm oceans |
| Sea Urchin, Giant, Black Spot | 1/2 | magical beast (aquatic) | temperate or warm oceans or coastlines |
| Sea Urchin, Giant, Glass Urchin | 9 | vermin (aquatic) | temperate or warm ocean or coastline |
| Sea Urchin, Giant, Great Diadem Urchin | 5 | vermin (aquatic) | temperate or warm oceans or coastlines |
| Sea Urchin, Giant, Hunter Urchin | 1 | vermin (aquatic) | temperate or warm ocean or coastline |
| Sea Urchin, Giant, Hunter Urchin | 1 | vermin (aquatic) | temperate or warm oceans
or coastlines |
| Sea Urchin, Giant, Ravenous Urchin Swarm | 2 | vermin (aquatic, swarm) | any coastlines or water |
| Sea Urchin, Giant, Spear Urchin | 4 | vermin (aquatic) | temperate or warm ocean or coastline |
| Sea Urchin, Giant, Spear Urchin | 4 | vermin (aquatic) | warm oceans or coastlines |
| Sea Worm, King Ragworm | 13 | vermin (aquatic) | any oceans |
| Seahorse, Giant Seahorse | 3 | animal (aquatic) | any oceans |
| Seahorse, Killer Seahorse | 5 | animal (aquatic) | any oceans |
| Seaweed Siren | 13 | magical beast (aquatic) | any coastlines |
| Seeded Creature, Seeded Lamia | 7 | undead (augmented monstrous humanoid) | temperate deserts |
| Seilenos | 19 | fey | temperate forests |
| Selkie | 5 | monstrous humanoid (aquatic, shapechanger) | cold oceans |
| Sentinel Hut | 8 | construct | any land (Irrisen) |
| Seps | 11 | magical beast | temperate or warm deserts or forests |
| Seps, Juvenile Seps | 2 | magical beast | — |
| Serpentfolk | 4 | monstrous humanoid | any land (usually jungles or underground) |
| Serpentfolk, Serpentfolk Bone Prophet | 11 | monstrous humanoid | any land (usually jungles or underground) |
| Serpentfolk, Serpentfolk High Priest | 14 | monstrous humanoid | any land (usually jungles or underground) |
| Serpentfolk, Serpentfolk Hunter | 6 | monstrous humanoid | any land (usually jungles or underground) |
| Serpentfolk, Serpentfolk Illusionist | 8 | monstrous humanoid | any land (usually jungles or underground) |
| Serpentfolk, Serpentfolk Reclaimer | 6 | monstrous humanoid | any land (usually jungles or underground) |
| Serpentfolk, Serpentfolk Spellblade | 13 | monstrous humanoid | any land (usually jungles or underground) |
| Serpentfolk, Serpentfolk Spy | 5 | monstrous humanoid | any land (usually jungles or underground) |
| Serpopard | 7 | magical beast | warm deserts or plains |
| Seru | 3 | magical beast | any land (jungles, swamps, or underground) |
| Set Guardian | 13 | construct | any (Osirion) |
| Seugathi | 6 | aberration | any underground |
| Seugathi, Seugathi Savant | 10 | aberration | any underground |
| Sha | 4 | magical beast | warm deserts |
| Shabti | 1/2 | outsider (native) | any |
| Shadow | 3 | undead (incorporeal) | any |
| Shadow Animal Lion | 4 | outsider (native) | warm plains |
| Shadow Collector | 8 | fey | any land |
| Shadow Creature, Shadow Roper | 13 | outsider (augmented aberration) | any underground |
| Shadow Fern | 4 | plant | any forests or underground |
| Shadow Mastiff | 5 | outsider (evil, extraplanar) | any |
| Shadow, Greater Shadow | 8 | undead (incorporeal) | any |
| Shadowfire Creature, Shadowfire Fire Elemental (Large) | 7 | outsider (elemental, extraplanar, fire) | any (Plane of Fire) |
| Shadowgarm | 2 | aberration (extraplanar) | any (Plane of Shadow) |
| Shadowy Lurker | 8 | undead (incorporeal) | any land (usually urban) |
| Shae | 4 | outsider (extraplanar) | any (Shadow Plane) |
| Shaghal | 8 | outsider (evil, extraplanar) | any (Abaddon) |
| Shalkeshka | 8 | magical beast (earth) | temperate and warm deserts and plains |
| Shambling Mound | 6 | plant | temperate forest or marshes |
| Shantak | 8 | magical beast | cold mountains |
| Shard Slag | 8 | ooze (fire) | any volcanoes or underground |
| Shark | 2 | animal (aquatic) | any ocean |
| Shark, Angustiden | 7 | animal (aquatic) | any ocean |
| Shark, Bull Shark | 2 | animal (aquatic) | any oceans |
| Shark, Dire Shark (Megalodon) | 9 | animal (aquatic) | any ocean |
| Shark, Great White Shark | 4 | animal (aquatic) | any oceans |
| Shark, Hammerhead Shark | 3 | animal (aquatic) | any ocean |
| Shark, Helicoprion | 6 | animal (aquatic) | temperate oceans |
| Shark, Jigsaw Shark | 1 | animal (aquatic) | any ocean |
| Shasalqu | 3 | magical beast | warm deserts |
| Shedu | 9 | magical beast | warm deserts |
| Shell Sentinel | 5 | construct | any (usually aquatic) |
| Shenzuzhou | 12 | undead | any |
| Shinigami | 17 | outsider (extraplanar, lawful) | any |
| Shining Child | 12 | outsider (evil, extraplanar) | any land (extraplanar) |
| Shining Child of Thassilon | 12 | outsider (evil) | any |
| Ship in a Bottle | 2 | construct | any |
| Ship in a Bottle, Bottled Armada | 6 | construct (swarm) | any |
| Ship Sentinel | 7 | construct | any water |
| Shipmind | 13 | ooze | any (Dominion of the Black ships) |
| Shissah | 4 | animal | warm deserts |
| Shobhad | 4 | monstrous humanoid | cold deserts or mountains |
| Shocker Lizard | 2 | magical beast | warm marshes |
| Shoggoth | 19 | ooze (aquatic) | cold aquatic or underground |
| Shotalashu | 2 | magical beast | any jungle (Castrovel) |
| Shredskin | 2 | undead | any land |
| Shriezyx | 4 | aberration | any |
| Shriezyx, Shriezyx Queen | 8 | aberration | any |
| Shrike Worm | 15 | aberration | any land or underground |
| Shulsaga | 3 | outsider (extraplanar) | any (Astral Plane) |
| Siabrae | 15 | undead (augmented humanoid, earth) | any blighted land |
| Sikari Macaque Swarm | 5 | animal (swarm) | warm forests |
| Siktempora, Misery Siktempora | 12 | outsider (chaotic, evil, extraplanar) | any (Dimension of Time) |
| Simurgh | 18 | magical beast | warm deserts or mountains |
| Sin Seeker | 2 | magical beast | any urban |
| Sinspawn | 2 | aberration | any ruins |
| Siren | 5 | magical beast | temperate or warm hills |
| Siren's Bed Anemone | 9 | vermin (aquatic) | warm coastlines or oceans |
| Sirrush | 21 | dragon (extraplanar, good) | any (Nirvana) |
| Sishkanset | 8 | outsider (extraplanar, incorporeal) | any land (Ethereal Plane) |
| Siyokoy | 10 | aberration (aquatic) | any ocean |
| Skapraun | 1 | fey | temperate or cold mountains |
| Skeleton, Armored Ogre Skeleton | 2 | undead | — |
| Skeleton, Four-Armed Mudra Skeleton | 1/2 | undead | — |
| Skeleton, Human Skeleton | 1/3 | undead | any |
| Skeleton, Multiplying T-Rex Skeleton | 9 | undead | — |
| Skeleton, Skeletal Champion | 2 | undead | any |
| Skeleton, Skeletal Mage | 5 | undead | any |
| Skeleton, Skeletal Mount | 1 | undead | — |
| Skeltercat | 4 | magical beast (shapechanger) | temperate forests, hills, or mountains |
| Skin Stealer | 2 | fey | any |
| Skincrawler | 1/2 | ooze | any |
| Skinstitch | 5 | construct | any land |
| Skinwalker | 1/2 | humanoid (shapechanger, skinwalker) | any forests, hills,
or mountains |
| Skirk Nettle | 6 | magical beast (extraplanar) | any tropical (First World) |
| Skittergoat | 1/2 | animal | temperate hills or plains |
| Skrimsl | 13 | magical beast (aquatic) | cold oceans |
| Skulk | 1 | humanoid (skulk) | any land or underground |
| Skull Ripper | 9 | construct
| any
|
| Skum | 2 | monstrous humanoid (aquatic) | temperate or cold aquatic or underground |
| Skunk | 1/4 | animal | temperate forests |
| Skunk, Giant Skunk | 3 | animal | temperate forests |
| Skvader | 1/2 | magical beast | temperate forest and hills |
| Slaugrak | 6 | outsider (chaotic, evil, extraplanar, native) | any underground |
| Sleipnir | 11 | magical beast | cold mountains |
| Slime Mold | 2 | ooze | temperate forests |
| Slithering Pit | 2 | ooze | any land |
| Slithering Tracker | 4 | ooze | any ruins or underground |
| Slurk | 2 | magical beast | temperate swamps or underground |
| Smoke Haunt | 4 | undead (fire) | cold forests and mountains |
| Smoke Sentinel | 9 | construct | temperate or warm forests |
| Smokeshade | 2 | aberration (extraplanar, incorporeal) | any (Plane of Shadow) |
| Snake Swarm | 2 | animal (swarm) | any |
| Snake Swarm, Venomous Snake Swarm | 4 | animal (swarm) | any |
| Snake, Asp | 2 | animal | warm deserts |
| Snake, Constrictor Snake | 2 | animal | warm forests, swamps, and fresh water |
| Snake, Emperor Cobra | 5 | animal | temperate or warm swamps |
| Snake, Giant Anaconda | 10 | animal | warm swamps |
| Snake, Venomous Snake | 1 | animal | any temperate or warm |
| Snallygaster | 3 | aberration | temperate forests or mountains |
| Snark | 1/4 | animal | any (First World) |
| Snowdrifter | 4 | aberration (air, cold) | cold hills |
| Solifugid, Albino Cave Solifugid | 4 | vermin | any underground |
| Solifugid, Giant Solifugid | 1 | vermin | warm deserts |
| Somalcygot | 12 | aberration | any (terrestrial vacuum) |
| Son of Perdition | 13 | outsider (chaotic, evil, extraplanar, incorporeal) | The Abyss |
| Sorico | 1 | animal | any deserts |
| Sorrow Stitcher | 8 | fey | any |
| Soucouyant | 8 | monstrous humanoid | any land |
| Soul Eater | 7 | outsider (evil, extraplanar) | any Outer Plane (Abaddon) |
| Soulbound Annihilator Robot | 17 | construct (robot) | any (Numeria) |
| Soulbound Doll | 2 | construct | any |
| Soulbound Mannequin | 7 | construct | any land |
| Soulbound Shell | 12 | construct | any land |
| Soulpierced | 17 | undead (incorporeal) | any land |
| Soulsliver | 2 | outsider (extraplanar, shapechanger) | any land (extraplanar) |
| Spartolos | 6 | undead | any |
| Spawn of Rovagug, Chemnosit (The Monarch Worm) | 23 | magical beast | any (Darklands) |
| Spawn of Rovagug, Festering Ulunat (The Unholy First) | 24 | magical beast | any (Sothis) |
| Spawn of Rovagug, Volnagur (The End-Singer) | 22 | magical beast | any (Casmaron) |
| Spawn of Rovagug, Xotani (The Firebleeder) | 20 | magical beast (fire) | any |
| Spawn of Yog-Sothoth | 10 | aberration (extraplanar) | temperate hills |
| Spectre | 7 | undead (incorporeal) | any |
| Spellgorger | 12 | ooze | any underground |
| Spellscar Fext | 7 | undead | any (Spellscar Desert) |
| Sphinx, Androsphinx | 9 | magical beast | warm deserts or hills |
| Sphinx, Criosphinx | 7 | magical beast | warm deserts or hills |
| Sphinx, Cynosphinx | 6 | magical beast | warm deserts and hills |
| Sphinx, Elder Sphinx | 16 | magical beast | warm deserts |
| Sphinx, Gynosphinx | 8 | magical beast | warm deserts and hills |
| Sphinx, Hieracosphinx | 5 | magical beast | warm hills |
| Spider Eater | 5 | magical beast | temperate forests |
| Spider, Drain Spider | 1/4 | vermin | any |
| Spider, Dream Spider | 1/2 | vermin | tropical forest or any urban |
| Spider, Giant Black Widow | 3 | vermin | any land |
| Spider, Giant Crab Spider | 1/2 | vermin | warm or temperate forests |
| Spider, Giant Spider | 1 | vermin | any |
| Spider, Giant Tarantula | 8 | vermin | any forests |
| Spider, Goliath Spider | 11 | vermin | any forests or swamps |
| Spider, Moon Spider | 2 | magical beast | temperate forest |
| Spider, Ogre Spider | 5 | vermin | temperate or cold hills or underground |
| Spider, Scarlet Spider | 1/4 | vermin | any land |
| Spider, Spider Swarm | 1 | vermin (swarm) | any |
| Spirit of Adoration | 15 | outsider (extraplanar, good) | any (extraplanar) |
| Spiroskek | 6 | magical beast | any underground |
| Spore Stalker | 7 | plant | warm swamps |
| Spriggan, Spriggan (Large Size) | 3 | humanoid (gnome) | any hills or forests |
| Spriggan, Spriggan (Normal Size) | 3 | humanoid (gnome) | any hills or forests |
| Spring-Heeled Jack | 3 | fey | any land |
| Sprite | 1/3 | fey | temperate forests |
| Sprite, Sprite Swarm | 5 | fey (swarm)
| temperate forests
|
| Squid | 1 | animal (aquatic) | any ocean |
| Squid, Giant Squid | 9 | animal (aquatic) | any ocean |
| Star Monarch | 9 | magical beast | any (Varisia) |
| Star Vampire | 6 | aberration | any air |
| Star-Spawn of Cthulhu | 20 | aberration | any |
| Steam Hog | 7 | magical beast | warm mountains |
| Steam-Powered Clockwork Dragon | 18 | construct (clockwork) | any |
| Stirge | 1/2 | magical beast | temperate and warm swamps |
| Storm Aurochs | 9 | magical beast | any sky |
| Stormghost | 15 | monstrous humanoid | cold mountains |
| Stranglereed | 9 | plant (aquatic) | warm rivers or lakes |
| Strix | 1/3 | humanoid (strix) | temperate mountains |
| Strix, Itaraak Champion | 9 | humanoid (strix) | temperate mountains |
| Strix, Strix Infiltrator | 3 | humanoid (strix) | temperate mountains |
| Strix, Strix Rokoa | 11 | humanoid (strix) | temperate mountains |
| Strix, Strix Voyager | 5 | humanoid (strix) | temperate mountains |
| Sturzstromer | 19 | outsider (earth, elemental, extraplanar, swarm) | any mountains (Plane of Earth) |
| Stygira | 7 | monstrous humanoid | temperate hills and underground |
| Stymphalide, Giant Stymphalidies | 8 | magical beast | warm mountains |
| Stymphalide, Stymphalides Swarm | 6 | magical beast (swarm) | warm plains and deserts |
| Stymphalidies | 8 | magical beast | warm plains or coastlines |
| Su | 8 | magical beast | any forests |
| Suli | 1/2 | outsider (native) | any |
| Sump Steward | 9 | plant | any swamp or underground |
| Sun Falcon | 4 | magical beast (fire) | warm deserts or mountains |
| Svartalfar | 8 | fey (extraplanar) | any (Shadow Plane) |
| Svathurim | 11 | monstrous humanoid (cold) | cold hills, mountains, or plains |
| Svirfneblin | 1 | humanoid (gnome) | any underground |
| Swamp Barracuda | 2 | animal (aquatic) | temperate or warm marshes |
| Swamp Mummy | 4 | undead | any swamps |
| Swan Maiden | 6 | fey (shapechanger) | temperate lakes or swamps |
| Swan, Trumpeter Swan | 1/3 | animal | temperate lakes or swamps |
| Switchback Jackal | 1/2 | animal | temperate and warm plains |
| Sylph | 1/2 | outsider (native) | any land |
| Syricta | 12 | aberration | any land |
| Syrinx | 1/3 | humanoid (syrinx) | temperate mountains (Arcadia) |