SG creating new hard content in a nutshell 
- 2021.07.15 09:01 (UTC+0)
SG : Here, you need to spam aoe attacks to kill the boss because it's covered in sealth and gets 90% dmg reduction.
Heirs : Oh, okay I'll use FS Tieria/Arby I invested a lot in them they should be able to nuke the crystals.
SG :No, no, no that's too easy you can't deal more dmg than 40% of crystal's hp(say hello to mini Turins!)
Heirs: Oh, o-okay I'll use Bellonas then.
SG: No,no, no Focus is forbidden. No Fighting Spirit either.
Heirs: Oh, o-okay I'll use Mercedes. Surely you removed the elemental weakness, right?
SG: YoU wAnT iT tO bE sO eAsY.
Overall, Sg hasn't learned anything since automaton tower(as evident with abyss). They always put these very restrictive requirements to pass contents like these and when you think you have the answer you get slap in the face in the form of
-another mechanic disabled
-5 other mechanics disabled
It's ridiculous how we have over 210 heroes but majority of them are not good in these endgame contents. I tried using Ray and he can't keep up. Why would he? His multpiers are equal to that of a 3* and he's a worse healer/cleanser than Achates. His s1 worse than Elena's so he can't cleanse both Freeze debuffs. Forget about building full earth comps. Only select few may be able to do that.
Injury and Boss' stackable Att/Spd force you to end the fight as soon as possible. If any of your teams isn't too well adjusted to one of the phases the just feed the boss with stacks.
It's basically a gear check. I just spent 50k mats and I didn't get a damn thing. Because even if you do get sth good it turns to garbage due to bad rolls. Every feature that was supposed to fix it didn't because we're tremendously restriced by the resources(cubes, gems are random most of the time, stones are rng too).
Overall, I knew this content is going to be a second abyss and I pass. Games are supposed t be fun and there's nothing fun in being unable to use 90% of heroes or to pass endgame content because gear acquisition is as bad as ever.
EDIT Just realized Vivian and Vildred are good for phase 1. Wow ge have only 2 suitable options in the sea of 200+. That's so many!