| Imp witch | 9 | Mob | |
| Imp witch | 10 | Mob | |
| Imp witch | 11 | Mob | |
| Imp witch | 12 | Mob | |
| Imp witch | 13 | Mob | |
| Imp witch | 14 | Mob | |
| Imp witch | 19 | Mob | |
| Inactive Scarecrow Troll | – | | Spawns |
 Infected Saxaul | 19 | | |
| Ingenious Poisoner | 6 | Mob | |
| Ingenious Poisoner | 7 | Mob | |
| Ingenious Poisoner | 8 | Mob | |
| Ingenious Poisoner | 9 | Mob | |
| Ingenious Poisoner | 10 | Mob | |
| Ingenious Poisoner | 11 | Mob | |
| Ingenious Poisoner | 12 | Mob | |
| Ingenious Poisoner | 13 | Mob | |
| Ingenious Poisoner | 14 | Mob | |
| Ingenious Poisoner | 19 | Mob | |
| Ingenious Poisoner | 19 | Mob | |
 Ingredient For Ale 01 | – | | Spawns |
 Ingredient For Ale 02 | – | | Spawns |
 Ingredient For Ale 03 | – | | Spawns |
| Initiated Apprentice | – | NPCQuest | |
 Intelligent Troll | – | NPCQuest | |
 Intoxicating Flower | – | | |
| Io | – | NPCQuest | |
| Iron Rivets | – | | Spawns |
| Isaac | – | NPC | |
| Isaac | – | NPC | |
| Isaac | – | NPC | |
| Isaac Active Object Inherit1 | – | | |
| Isaac Active Object Inherit2 | – | | |
| Isaac Active Object Inherit3 | – | | |
 Isopropyl Alcohol | – | | Spawns |
| Ivie Clarkson | – | NPCVendorQuest | VendorSpawns |
 J'brahah | – | NPCQuest | |
| Jack | – | Quest | |
| Jade Falcon | – | | |
| Jade Quickshade | – | NPC | VendorSpawns |
| Jahri Bubbler | – | | Spawns |
| Jahri Roots | – | NPCQuest | VendorSpawns |
| Jasper Wilde | – | NPCQuest | |
| Jax | – | NPC | Vendor |
| Jayla | – | NPCQuest | |
| Jeffery Schaefer | – | NPC | Vendor |
| Jennifer Davyna | – | NPC | VendorSpawns |
| Jennifer Davyna | – | NPC | VendorSpawns |
| Jerry | – | NPC | |
| Jett Stringer | – | NPC | VendorSpawns |