Cage

Description
The Cage is an item that can be bought from the shop for an initial price of 250 Gems. It stores up to 4 minions and can be upgraded further.

Legendary minions can not be put in the Cage, nor can the NecroMerger, or any items, since those would go in the Crate.

If the Cage is empty, it can be fed to the Devourer and reclaimed from the Shop at any time (given there is free space in the lair.) The same goes for prestiging.

Upgrades
You can buy additional 6 slots using gems (+2 each time for 500/750/1000 gems) or use The Architect to buy 5 additional slots. The maximum is 15 slots.