| Cloaked zealot (Normal mode) [] | 45–55 | 1/61,440 |
| Cockatrice [] | 1 | 1/4,096 |
| Cockatrice [] | 45–55 | 1/3,355,443.2 |
| Cockroach drone [] | 1 | 1/1,365.33 |
| Cockroach drone [] | 45–55 | 1/1,118,481.07 |
| Cockroach soldier [] | 1 | 1/1,170.29 |
| Cockroach soldier [] | 45–55 | 1/958,698.06 |
| Cockroach worker [] | 1 | 1/1,638.4 |
| Cockroach worker [] | 45–55 | 1/1,342,177.28 |
| Columbarium key [] | 4 | 9/329 |
| Commander Zilyana (Hard mode) [] | 20–30 | 8/128 |
| Commander Zilyana (Hard mode) [] | 45–55 | 1/40,960 |
| Commander Zilyana (Normal mode) [] | 1 | 1/4,096 |
| Commander Zilyana (Normal mode) [] | 45–55 | 1/40,466.03 |
| Cooper (Normal mode) [] | 45–55 | 1/61,440 |
| Corbicula rex [] | 5 | Common |
| Corporeal Beast [] | 15 | 22/512 |
| Corporeal Beast [] | 1 | 1/3,276.8, 10 rolls |
| Corporeal Beast [] | 45–55 | 1/2,684,354.56, 10 rolls |
| Corrupted dust devil [] | 45–55 | 1/61,440 |
| Corrupted kalphite guardian [] | 45–55 | 1/61,440 |
| Corrupted kalphite marauder [] | 45–55 | 1/61,440 |
| Corrupted lizard [] | 45–55 | 1/61,440 |
| Corrupted scarab [] | 45–55 | 1/61,440 |
| Corrupted scorpion [] | 45–55 | 1/61,440 |
| Corrupted worker [] | 45–55 | 1/61,440 |
| Crassian Leviathan (Normal mode) [] | 45–55 | 1/61,440 |
| Crassian scout (Normal mode) [] | 45–55 | 1/61,440 |
| Crassian scuttler (Normal mode) [] | 45–55 | 1/61,440 |
| Crassian warrior (Normal mode) [] | 45–55 | 1/61,440 |
| Crawling hand [] | 1 | 1/4,096 |
| Crawling hand [] | 45–55 | 1/3,355,443.2 |
| Crocodile akh [] | 45–55 | 1/61,440 |
| Croesus (Active) [] | 5–15 | 50/1,000 |
| Crystal chest [] | 3 | 600/6,801 |
| Crystal chest (Prifddinas) [] | 3 | 600/6,801 |
| Crystal geode [] | 1 | 6/20 |
 Crystal impling[] | 10 | 25/500 |
| Crystal impling jar [] | 10 | 25/500 |
| Crystal Shapeshifter (Magic) [] | 45–55 | 1/61,440 |
| Cyclops [] | 1 | 1/3,200 |
| Cyclops [] | 45–55 | 1/2,621,440 |
| Cyclops [] | 45–55 | Very rare |
| Cyclops (God Wars Dungeon) [] | 1 | 1/3,200 |
| Cyclops (God Wars Dungeon) [] | 45–55 | 1/2,621,440 |
| Cyclossus [] | 1 | 2/100 |
| Cyclossus [] | 45–55 | 1/81,920 |
| Dagannoth (Lighthouse) [] | 1 | 1/8,192 |