This event is a combination of 2 events, gacha pulling and raid boss.
Gacha one is simple and as usual. Play event stage to get currency and pull awesome items.
Raid boss is a beef up of old raid boss where you have 5 turns for each team to finish the boss before the battle comes to a draw. However this time it got a nice tweak.
You fight the boss with your team 1 as a main one. Team2-4 will be assist as part of ally team.
Boss got 3 phases, easy, normal, and hard (or rather, broken) You got 5 turns for each phase to finish them. Each turn has 3 steps
1. Your ally turn: Ally refer to team 2,3,4, your friend in the list, or Nazuna's assist. Nazuna's assist has 3 options. Deal small damages (around 60k), heal your party for 20k, and the last is reduce damage you take by 50% (1 turn)
2. Team 1 turn: This is the main game, make sure they are the strongest team you can muster. If they lost, that's it.
3. Nidhogg's turn: I don't know what the requirement but this guy or his buddy can boost their atk by 60% if they want, and effect can stack. Your full-amped rainbow can be 1-shot easily.
If by 5 turns you can't defeat it and you still standing, it's a draw. Any pests you defeat is counted towards total defeated numbers whether you defeat all 7 or just 1.
I might miss something or some info might be a bit off. But pretty sure I got most right.