What is in the Slime Boxes?

[Karin]

One Mysterious Slime Cache holds:
Two slimes that can be epic or legendary slimes plus either coins, embers, essence or commander emblems.

One Ordonfell Cache holds:
One mythic slime.

[TheEDM]

what can we do with slimes?

[Karin]

They are a sort of joker you can use to evolve your heroes if you don't have enough of the heroes. More here: https://forum.honorboundgame.com/thread-7.html