ToME: the Tales of Maj'Eyal

So, there is a chest, if I open it, it look like under lid it has another chest.
If I re-enter level, chest looks closed again, I can open it again, and take what it had.
In this case it was gem, so I can get infinite amount of them.

Also, found a chest that spawn same enemy with boss-rank.
When spawned, he already has status effect from previous fight, and I can open chest without need to re-enter map.

And all three times I have identical loot.