<<Disclaimer: this is no rant, mere ideas which could make things even more fun >>
I will be using references to the current Palace of the Dead, unaware of any improvements comming for future itterations of the Deep Dungeon feature.

1. For the higher levels of Deep Dungeon, add the option of character customisation, with some form of progression to it. (lvl51+ or lvl101+, depending on where you want to draw the line)
Customisation options: Pick a handfull of abilities for every class and allow those abilities to be customised through some sort of legendary gem system, but said customisations only work within the Deep Dungeon. Said Legendary gems can be upgraded to increase the potency of their effect.

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