The key to defeating Sorath is to make sure she has HP Burn. And in order to make sure the HP Burn stays on her, it’s better to kill the spiderlings first (as otherwise Sorath will pass debuffs over to them). Sorath needs to have HP Burn on her when she dies, otherwise she will revive herself. Furthermore, her DEF and RESIST are increased significantly while she isn’t under HP Burn, so you need to make sure you have very high ACC to place HP Burn on her.
A niche strategy is to bring Champions who can block revive (e.g. Foli or Fenax) however the timing required (to ensure they’re the ones killing Sorath) makes it quite difficult to do this strategy reliably.
Team compositions:
The team composition I use is as follows:
Underpriest Brogni (lead): Brogni is awesome against Sorath, with an HP Burn on his A1, Shields that can’t be removed to protect your team, and even some debuff removal.
Sethallia: Sethallia brings great Turn Meter increases, healing, and an HP Burn on her A1. Sethallia, with the right setup, can solo Sorath.
Drexthar Bloodtwin: Drexthar is fantastic against Sorath, with a chance to HP Burn every time Sorath attacks.
Doompriest: I bring Doompriest for the clutch healing and debuff removal.
Kreela Witch Arm: I bring Kreela along for her ally attack skill, which gives Brogni, Sethallia, and Drexthar a chance to land their HP Burns.
Alternate, more achievable comp (no Legendary and no Void Epic/Lego):
High Khatun (lead): Speed aura, turn meter increases, Increase SPD, and Decrease SPD on the enemy.
Coffin Smasher: Semi-reliable HP Burn and helps keep your team alive with his passive that reduces the damage from AoE attacks for your team.
Reliquary Tender: Brings in healing, debuff removal, and revives to keep you alive.
Bulwark: Reliable HP Burn (100% when booked up) plus a chance to extend debuffs.
Apothecary: Great healer and Increase Turn Meter / Increase SPD.
SORATH THE FROST SPIDER SKILLS
A1: Whiteout [ATK]. Attacks all enemies. Places a 50% [Decrease ACC] debuff for 2 turns.
A3: Absolute Zero [ATK]. Removes all buffs from enemies, then attacks them. Has a 100% chance of placing [Freeze] debuff for 1 turn. The chance decreases to 50% if Sorath is under a [HP Burn] debuff. Fills Sorath’s Turn Meter by 20% for each [Freeze] debuff placed by this skill.
Passive 1: Frozen Lymph. When attacked, has a 20% chance of placing a [Freeze] debuff on the attacker for 1 turn. Increases Sorath’s DEF and RESIST if Sorath is not under [HP Burn] debuff.
Passive 2: Purge by Flame. Revives Sorath the Frost Spider with 50% HP, a full Turn Meter, and all skill cooldown reset if Sorath is killed while not under [HP burn] debuff. Also spawns 2 spiderlings. Sorath can have a maximum of 2 Spiderlings in battle at any time.
Passive 5: Almighty Strength. Damage from skills that scale based on enemy MAX HP cannot exceed 10% of the boss’ MAX HP when attacking the boss.
Spiderlings [2 Minions]. Removes all debuffs from Sorath. Instantly transfer [Decrease DEF] debuff and [Weaken] debuff to this spiderling if not under leech. Will convert debuffs to weaker version on transfer.