What does the Dark mirror levels?

[Wildflower]

besides the benefits. like do they increase enemy health or damage or is it just I get cool stuff for beating the game in that mode?

[Arc]

As you get higher it spawns more variants of enemies, gives you more options before (starting with two free items of your choice out of a pool, starting with free skulls) runs or during (can have 2 inscriptions active without using items, gambling in shop, trading skulls for stat points) and spawns more of the dark enemies you can trade for dark powers with more dark powers unlocking on higher modes.
DM7 is probably the most important one since that's when you get the extra inscriptions which opens up builds a lot.

[Wildflower]

Originally posted by Arc:

As you get higher it spawns more variants of enemies, gives you more options before (starting with two free items of your choice out of a pool, starting with free skulls) runs or during (can have 2 inscriptions active without using items, gambling in shop, trading skulls for stat points) and spawns more of the dark enemies you can trade for dark powers with more dark powers unlocking on higher modes.
DM7 is probably the most important one since that's when you get the extra inscriptions which opens up builds a lot.

Thanks, the wiki was no help. someone should really update it with all this info