Lord of Heroes 7-11 Nightmare

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Timestamps:
0:11 Wave 1
1:25 Wave 2
3:06 Wave 3
Wave 3 boss, need to stun/freeze/petrify the Glacier Crystals to prevent their lethal attacks. The Glacier Crystals must be killed first to weaken the boss. If you have DLucilicca you can directly drain boss hp.
Roles:
WAstrid - max S3. Refined relic recommend
DKHelga - replaceable with 5x mass attack DPS or just use DLucilicca
WKrom - replaceable with other action gauge hero (WJoshua recommend)
FLyn - recommend for her attack buff but replaceable with generous burst gauge sniper
LMu - recommend for her revive ability and action gauge increase
Builds:
WAstrid - 6 revenge. 4 hp 1 speed 1 debuff rate
DKHelga - 6 pierce. 4 atk 2 crdmg
WKrom - 2 aegis 4 bulwark. 2 hp 2 def 2 speed
FLyn - 6 surge. 2 hp 2 def 2 speed
LMu - 4 heal 2 life. 4 hp 1 speed 1 resistance