The I.D.P.D. (Inter-Dimensional Police Department) is a group of enemies set on killing the player when they reach a certain level of power.
Gameplay-wise, they are designed to be the equivalent of the player, but using tech to augment their abilities rather than mutations. All I.D.P.D. troops can damage enemies that aren't in the I.D.P.D. and can be damaged by their projectiles and Fire Traps like the player would. When your character doesn't move/shoot and the I.D.P.D. units don't get hurt, they won't attack you like all other enemies would. Details of each unit can be seen on their individual pages.
I.D.P.D. portals only spawn Grunts by default. After enough I.D.P.D. portals open during a run Inspectors and eventually Shielders will have a chance of spawning. So the more portals appear throughout the run, the tougher units can spawn. There are multiple events that cause I.D.P.D. units to spawn:
- When you damage a Proto Statue or fully charge it.
- When you open an I.D.P.D. Ammo Chest.
- If you get a crown, they will spawn right after you exit the Crown Vault.
- If you start with a crown, they will spawn on 1-1.
- Multiple I.D.P.D. units can spawn in during the Lil' Hunter boss fight. He can only summon Grunts pre-loop and every I.D.P.D. unit during the loops.
- A random amount of I.D.P.D. units spawn in the Palace area on 7-1 and 7-2
- Four I.D.P.D. portals open in the Campfire area (0-1).
- The I.D.P.D. can appear on every area except the Crown Vault and 7-3 if you are playing as Rogue.
- After looping the game I.D.P.D. portals appear on every area except the Crown Vault and 7-3. Two I.D.P.D. portals appear after you kill a certain amount of enemies in a level. The moment they open is randomized and anywhere between 20%-80% of all enemies killed on that stage.
I.D.P.D. Vans appear only after you loop the game. The Van will burst through a larger version of the blue I.D.P.D. portals and charge horizontally through terrain, unloading a large number of troops after it comes to a stop.
If you killed an I.D.P.D. unit on a level, the next I.D.P.D. spawn will be replaced by an I.D.P.D. Van. Each loop adds an additional Van that will teleport in after the first. The moment any I.D.P.D. portals or Vans appear is randomized and anywhere between 20%-80% of all enemies killed on that stage. For example, on loop 2, the first spawn will be a pair of portals which open after you've killed 27% of enemies, then a Van will teleport in on 45% and a second Van on 78%. All of the % values are randomized from 20% to 80% and are different for each area.
Getting behind the Van while it's moving (lights have to be on) and pressing "E" will teleport the player to the I.D.P.D. HQ secret area.
Also appearing on loops are Elite I.D.P.D. which are upgraded versions of the regular I.D.P.D. units. They start teleporting in after the first Campfire area (1st loop 0-1). If an I.D.P.D. portal opens triggered by any of the events listed above, there's a chance that a single Elite I.D.P.D. unit spawns from it instead of regular I.D.P.D.. This also applies to units unloaded by I.D.P.D. Vans. Groups of Grunts will also be replaced by a single Elite unit.
The spawn chance equals 1/(6 - number of loops). It ranges from 20% on loop 1 to 40% on loop 2. Details of each unit can be seen on their individual pages.
After the Campfire area on your third loop something bad happens and all I.D.P.D. become mutated. I.D.P.D. Freaks will replace all regular and Elite I.D.P.D. units. Vans will unload I.D.P.D. Freaks and instantly explode after that. I.D.P.D. Freaks will also resurrect from enemy corpses which continuously happens on its own if at least one enemy is left alive on the level.
- The I.D.P.D's home dimension is the only reality where the apocalypse did not occur. This is why they do not drop any radiation on death.
- JW has discussed their intent as being a preemptive strike to kill the player before they pose a threat to their dimension.
- The I.D.P.D. speak a language that the mutants don't understand.