Just beat Void Erosion Purge using only Sharen (as a challenge). Here's the build and some thoughts on the game mode.

Stages 1 thru 10 were easy and forgettable, but, from 11 thru 20, this game mode starts to offer a bit of a challenge.

For stages 1 thru 10, I could just rush into the middle of enemies and survive just fine, but from stage 11 on, I started getting killed for my recklessness.

I had to play defensively for once, which was new and very engaging, with casting skills, hiding behind cover and being aware of my surroundings. All enemies posed some threat to my health, except trash melee enemies. Face-tanking trash ranged mobs just wasn't viable anymore. Also, I had to prioritize targets, because, at higher levels, some enemies present a much higher threat than others.

At stage 13 I couldn't kill one elite enemy type with a single Invisibility+Area Suppression, and more elites enemies managed to survive that combo over the next stages with some bosses being a bit tanky as well (but some of that was due to me using Sharen against enemies/bosses with moderate-to-high electric resistance).

Thankfully, the game shows how many kills you need to get to summon the boss along with the timer in a pretty intuitive bar at the side of the screen. You're behind on your time? Then play more aggressively or restart. You have a lot of spare time? Then you can play it safer for while, because the last waves of enemies+boss can be brutal.

Also, I love that this has to be done solo. Maybe this will filter out people who aren't ready for this type of content (be it due to poor builds or lack of skill), making coop play more fun with little to no bad teammates (elite enemies and bosses scale to the number of people in the match, so group play is harder than solo, if anyone wants a challenge).

I like that we have a penalty for dying that increases with each death, but I'm afraid that only matters for first clears and that this game mode will just delve into mindless killing from the second clear on. I wish we got more rewards if we kept avoiding death penalties to maintain a low time after the first clear.

I won't get into the grind for core binders and related mats, because that's another can of worms.

Overall, I think this is a promising endgame mode that just needs a few tweaks. Looking forward to stages 21-30.