| Name | CR | Type | Environment |
| Kaicharek | 4 | magical beast (extraplanar) | any (Blood Vale) |
| Kaiju, Agyra | 27 | magical beast (air, kaiju) | warm mountains |
| Kaiju, Bezravnis | 26 | magical beast (earth, kaiju) | warm deserts |
| Kaiju, Mogaru | 28 | magical beast (kaiju, water) | warm forests or water |
| Kaiju, Varklops | 30 | magical beast (fire, kaiju) | warm mountains |
| Kaiju, Vorgozen | 29 | ooze (kaiju, water) | warm swamps |
| Kaiju, Yarthoon | 25 | magical beast (air, kaiju) | any cold (the world’s moon or outer space) |
| Kakuen-Taka | 14 | outsider (chaotic, evil, extraplanar, swarm) | any (the Worldwound) |
| Kamadan | 4 | magical beast | temperate or warm plains |
| Kamaitachi | 13 | fey (air) | any |
| Kami, Dosojin | 7 | outsider (kami, native) | any land |
| Kami, Dunagh | 4 | outsider (incorporeal, kami, native) | any urban |
| Kami, Fukujin | 3 | outsider (kami, native) | any |
| Kami, Jinushigami | 20 | outsider (earth, kami, native) | any |
| Kami, Kaminari | 17 | outsider (air, kami, native) | temperate skies, hills, and mountains |
| Kami, Kodama | 5 | outsider (kami, native) | any forest |
| Kami, Shikigami | 2 | outsider (kami, native) | any |
| Kami, Suijin | 14 | outsider (kami, native, water) | any water |
| Kami, Toshigami | 15 | outsider (kami, native) | any land |
| Kami, Zuishin | 10 | outsider (kami, native) | any |
| Kanabo, Honored of Kaoling | 4 | outsider (goblinoid, native) | — |
| Kangaroo | 1/2 | animal | temperate hills or plains |
| Kappa | 2 | monstrous humanoid (aquatic) | any lake or river |
| Kapre | 10 | plant | warm or temperate forests |
| Karkadann | 4 | magical beast | warm deserts |
| Karkinoi | 6 | monstrous humanoid (aquatic) | any water |
| Karkinoi, Karkinoi Brood Swarm | 4 | monstrous humanoid (aquatic, swarm) | any water |
| Karumzek | 4 | outsider (evil, extraplanar, shapechanger) | any (Axis) |
| Kasatha | 1/2 | humanoid (kasatha) | warm deserts |
| Kasthezvi | 12 | aberration (shapechanger) | any underground (Kaer Maga) |
| Katroome | 1 | magical beast | any forest |
| Kawa Akago | 3 | plant | temperate marshes or rivers |
| Kech | 3 | monstrous humanoid | warm forests |
| Keeper of the Yellow Sign | 6 | undead | any land |
| Kelpie | 4 | fey (aquatic, shapechanger) | any water |
| Kelpie’s Wrath | 15 | outsider (chaotic, extraplanar, water) | any water |
| Kerakinsi | 4 | monstrous humanoid | warm swamps |
| Ketesthius | 13 | magical beast (aquatic) | any oceans or coastlines |
| Keulia | 1/4 | animal | temperate or warm forests |
| Khaei | 3 | monstrous humanoid | any underground (beneath Kaer Maga) |
| Khala | 17 | dragon (cold) | any cold |
| Khardajeen | 14 | aberration | any underground |
| Kijimuna | 2 | humanoid (goblinoid) | temperate or warm forests or coasts |
| Kikimora | 5 | fey | any urban |
| Kikituk | 13 | construct | any |
| Kirin | 7 | magical beast (air) | any |
| Kirrix | 3 | magical beast | any underground |
| Kitsune | 1/2 | humanoid (kitsune, shapechanger) | temperate forests, hills, or mountains |
| Kobold | 1/4 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Battle Master | 6 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Blade | 3 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Bomber | 1 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Chieftain | 8 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Devilspeaker | 7 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Guilecaster | 5 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Master Trapper | 4 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Monster Wrangler | 1 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Scalecaster | 1/2 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Sniper | 1/2 | humanoid (reptilian) | temperate underground or deep forest |
| Kobold, Kobold Yapper | 7 | humanoid (reptilian) | temperate underground or deep forest |
| Kokogiak | 12 | magical beast
| cold coastlines, hills, or plains
|
| Kongamato | 15 | dragon | tropical forests |
| Korir-Kokembe | 10 | dragon | warm jungles (Mwangi Expanse) |
| Korred | 4 | fey | temperate forests |
| Kraken | 18 | magical beast (aquatic) | any ocean |
| Kraken, Qwoshokk | 20 | magical beast (aquatic) | — |
| Krampus | 21 | monstrous humanoid | any |
| Kravyad | 7 | magical beast | warm swamps |
| Krenshar | 1 | magical beast | temperate forests or plains |
| Kudimmu | 16 | plant | any land |
| Kurobozu | 6 | undead | any |
| Kuru | 1/2 | humanoid (kuru) | any coastal |
| Kyrana | 3 | dragon (fire) | any underground or warm deserts |
| Kyton | 6 | outsider (evil, extraplanar, kyton, lawful) | any |
| Kyton Demagogue, Inkariax | 26 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Apocrisiarius | 7 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Apostle Kyton | 12 | outsider (augmented humanoid, kyton, native) | any land |
| Kyton, Augur | 2 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Cantor | 9 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Ephialtes | 16 | outsider (evil, extraplanar, kyton, lawful) | any (Shadow Plane) |
| Kyton, Eremite | 20 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Interlocutor | 12 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Lampadarius | 4 | outsider (evil, extraplanar, kyton, lawful) | any (Shadow Plane) |
| Kyton, Libitinarii | 13 | outsider (cold, evil, extraplanar, kyton, lawful) | any (Shadow Plane) |
| Kyton, Oitos | 11 | outsider (evil, extraplanar, kyton, lawful) | any (Shadow Plane) |
| Kyton, Ostiarius | 5 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Phylacator | 18 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Sacristan | 10 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Suffragan | 5 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |
| Kyton, Termagant | 17 | outsider (evil, extraplanar, kyton, lawful) | any (Plane of Shadow) |