| Skulk | 0.5 | Humanoid | Medium | 14 | 18 | | chaotic neutral | | Mordenkainen's Tome of Foes | | | | | | |
| Skull lasher of myrkul | 1 | Humanoid (human) | Medium | 12 | 32 | | neutral evil | | Adventures (Descent into Avernus) | | | | | | |
| Skull lord | 15 | Undead | Medium | 18 | 105 | | lawful evil | | Mordenkainen's Tome of Foes | | | | | | |
| Slaad tadpole | 0.12 | Aberration | Tiny | 12 | 10 | | chaotic neutral | | Monster Manual | | | | | | |
| Slithering tracker | 3 | Ooze | Medium | 14 | 32 | swim | chaotic evil | | Volo's Guide to Monsters | 16 | 19 | 15 | 10 | 14 | 11 |
| Smoke mephit | 0.25 | Elemental | Small | 12 | 22 | fly | neutral evil | | Monster Manual (SRD) | 6 | 14 | 12 | 10 | 10 | 11 |
| Solar | 21 | Celestial | Large | 21 | 243 | fly | lawful good | Legendary | Monster Manual (SRD) | 26 | 22 | 26 | 25 | 25 | 30 |
| Soul monger | 11 | Humanoid (elf) | Medium | 15 | 123 | | neutral | | Mordenkainen's Tome of Foes | | | | | | |
| Spawn of kyuss | 5 | Undead | Medium | 10 | 76 | | chaotic evil | | Volo's Guide to Monsters | | | | | | |
| Spectator | 3 | Aberration | Medium | 14 | 39 | fly | lawful neutral | | Monster Manual | 8 | 14 | 14 | 13 | 14 | 11 |
| Specter | 1 | Undead | Medium | 12 | 22 | fly | chaotic evil | | Monster Manual (SRD) | 1 | 14 | 11 | 10 | 10 | 11 |
| Spellcaster healer lvl 1 | 0 | Humanoid (any race) | Medium | 12 | 9 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster healer lvl 2 | 0 | Humanoid (any race) | Medium | 12 | 13 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster healer lvl 3 | 0 | Humanoid (any race) | Medium | 12 | 18 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster healer lvl 4 | 0 | Humanoid (any race) | Medium | 12 | 22 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster healer lvl 5 | 0 | Humanoid (any race) | Medium | 12 | 27 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster healer lvl 6 | 0 | Humanoid (any race) | Medium | 12 | 31 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster mage lvl 1 | 0 | Humanoid (any race) | Medium | 12 | 9 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster mage lvl 2 | 0 | Humanoid (any race) | Medium | 12 | 13 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster mage lvl 3 | 0 | Humanoid (any race) | Medium | 12 | 18 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster mage lvl 4 | 0 | Humanoid (any race) | Medium | 12 | 22 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster mage lvl 5 | 0 | Humanoid (any race) | Medium | 12 | 27 | | any alignment | | Essentials Kit | | | | | | |
| Spellcaster mage lvl 6 | 0 | Humanoid (any race) | Medium | 12 | 31 | | any alignment | | Essentials Kit | | | | | | |
| Spider | 0 | Beast | Tiny | 12 | 1 | | unaligned | | Monster Manual (SRD) | 2 | 14 | 8 | 1 | 10 | 2 |
| Spined devil | 2 | Fiend (devil) | Small | 13 | 22 | fly | lawful evil | | Monster Manual | | | | | | |