| Name | CR | Type | Environment |
| Kaa-leki | 8 | humanoid (kaa-leki, plantlike) | any (Hawanna) |
| Kaion | 2 | animal | mountains, urban, or vacuum (Diaspora) |
| Kaion | 2 | animal | mountains, urban, or vacuum (Diaspora) |
| Kaion, Multipole | 11 | animal | mountains, urban, or vacuum (Diaspora) |
| Kalo, Kalo Deepspeaker | 5 | monstrous humanoid (aquatic) | any aquatic (Kalo-Mahoi) |
| Kalo, Kalo Sharkhunter | 2 | monstrous humanoid (aquatic) | any aquatic (Kalo-Mahoi) |
| Kalo-mahoi Bloom | 13 | plant (aquatic, cold) | aquatic |
| Kami, Chinjugami | 16 | outsider (kami, native) | any |
| Kami, Toshigami | 13 | outsider (kami, native) | any land |
| Kami, Tsukumogami | 4 | outsider (kami, native) | any |
| Kaukariki | 1 | magical beast | warm forests (Castrovel) |
| Kavearin | 10 | outsider (extraplanar) | any (Negative Energy Plane) |
| Kayal | 7 | outsider (native) | any (Shadow Plane) |
| Keji Swarm | 10 | animal (swarm) | any air (Liavara) |
| Khefak | 1/3 | vermin | any (Akiton) |
| Khefak, Thasteron Khefak | 3 | vermin | any (Akiton) |
| Khulan, Ascendant | 12 | fey (fire, incorporeal) | any mountains or underground (Akiton) |
| Khulan | 7 | fey (fire, incorporeal) | any mountains or underground (Akiton) |
| Kiirinta | 3 | fey | any (Stabrisis-14) |
| Kiirinta, Shaman | 6 | fey | any (Stabrisis-14) |
| Kish | 4 | humanoid (kish) | any (Nejeor VI) |
| Klikharp, Hatchling | 1/2 | vermin | any |
| Klikharp, Mount | 5 | vermin | any |
| Kothama | 10 | magical beast (cold) | any (Vesk-7 or Vesk-8) |
| Kothama, Kothama Ascendant | 14 | magical beast (cold) | any (Vesk-7 or Vesk-8) |
| Kriegakos | 8 | animal | any air (Liavara) |
| Ksarik | 4 | plant | temperate or warm forests (Castrovel) |
| Kunnid | 5 | magical beast | any |
| Kurobozu | 9 | undead | any |
| Kyokor | 20 | magical beast (colossus) | any (Daimalko) |