Treasure seeker level 3

[DGDobrev]

Benefits are huge

Get it to 3/2 for 8 rage. For the measly amount of 24 rage per battle you will lay your hands on tons of money, spells, runes, and wanderers' scrolls.

[Zechnophobe]

Basically, getting the third upgrade for it is only really useful in getting the upgrades after that. You can get the cost reduced back down to 8, and eventually find 3 treasures per combat, which can be nice.

Also note that you get more experience from better upgraded abilities (Not that treasure searching at end of combat will give much xp).