| Name | CR | Type | Environment |
| Calecor | 17 | fey | any |
| Cargo Creep | 4 | aberration | any |
| Carnivorous Crystal | 11 | ooze (earth, extraplanar) | any (Plane of Earth) |
| Carrion Dreg | 4 | undead | any |
| Caypin | 6 | magical beast (aquatic) | any swamp |
| Cephalume | 2 | aberration (plantlike) | any (Luminar) |
| Cerebric Fungus | 3 | plant | any |
| Cerebric Fungus, Cerebric Fungus Voyager | 9 | plant | any |
| Chomurk | 8 | magical beast | vacuum |
| Colour out of Space | 10 | ooze (incorporeal) | any |
| Comanide | 7 | fey | any |
| Contemplative | 2 | monstrous humanoid | any urban (Akiton) |
| Contemplative, Contemplative Mentor | 18 | monstrous humanoid | any urban (Akiton) |
| Corpsefolk, Corpsefolk Marine | 7 | undead | any (Eox) |
| Corpsefolk, Corpsefolk Operative | 3 | undead | any (Eox) |
| Crate Fiend | 3 | vermin | any urban or land (Taekah III) |
| Creeping Shade | 8 | outsider (incorporeal) | any (Shadow Plane) |
| Crest-Eater | 4 | magical beast | warm deserts (Kasath) |