Going Under

This achievement is unlocked for killing a mimic item cube. The mimic cubes don't start spawning until the second half of the game. This occurs after you have completed four dungeons and they are reset for story reasons. The mimic cubes do not appear to spawn when dropped off by drone but instead must be found hanging around in rooms.

I got this achievement within the first floor after the mid-point of the game in Joblin and they seem to have a decently high spawn rate.

Hungry Boxes are Cubicle box mimics that only begin to spawn in True Founder dungeons. However, they're rare; by the time I unlocked all skills and otherwise completed the rolodex, I had only seen one by pure chance.

The main way to tell if a box is a Hungry Box is that you cannot pick it up like a normal box. You can push it around all you like without triggering it, but you won't have the prompt to pick it up.

The best way to quickly check for Hungry Boxes is to defeat Vested Marv on floor 999 of Cubicle, then pause the game and abandon the run.



Re-entering the dungeon will put you on Floor 1000 with Marv's Union Buster, with the next room being a large skill shop staffed by all three merchants. Directly to your left is a Cubicle box that always spawns a blank card for the rolodex. Behind the merchants are boxes, and a Hungry Box can spawn here. You can either swing at the stack to trigger a potential box, or try to pick it up so you know if it's a box, which can be handy if going for the rolodex. If no box spawns, abandon the run and re-enter Floor 1000.

Video guide credit to TheAlmondButter.