Basically it's for those times when you have the perfect run and finish the dungeon as a god with a ton of potions left over but nothing left to fight.
Like today I was playing a fireball assassin on Doubledoom, and was lucky enough to spawn mage plate, fire heart, Dracul AND Mysteria in the same dungeon. With the battlemage ring I took in the result was 70 damage stacking fireballs, from a 35 mana pool with a whole lot of mana potions to spare.

I think everyone has had those runs where everything just lines up perfectly and you destroy the boss in 2 hits and you're left feeling a bit empty cause you've created this perfectly crafted demi-god of a hero and have nothing left to do with him (except make a forum post to brag hahaha).