
Treasure chests
In the 1st treasure chest of a run, and in every 5th one after it: the 1st, 6th, 11th, 16th, 21st and 26th. An Arcana chest counts as one. The banner says +1 DIAMOND!
Diamonds are the game's rarest treasure. You keep them for good, and the lobby shows them just above your gold. A run finds only a few.

In the 1st treasure chest of a run, and in every 5th one after it: the 1st, 6th, 11th, 16th, 21st and 26th. An Arcana chest counts as one. The banner says +1 DIAMOND!

In the first ancient chest you open in a run. A zone's chest is not one of them: it has its own.
Break a zone's boss structure and kill its boss. The diamonds show on the ancient chest it leaves.