Boss Guide: Ch16-1 (Gotterdammerung)

Additional Guides

Enemy Layout

Fatal Battle 1/1		216,833 Surt Fenrir
		239,420 Surt Fenrir
		311,698 Surt Fenrir

Section 16: Beyond the Gaze (1/3) AP - 25

Drops	Giant's Ring x3 (100%)
Rewards

Boss Statistics

	Sigurd (Mandatory Support) Lv90 NP5 10/10/10
Battle Start		"Slash the flame apart!": Increase NP Strength by 100% [Permanent, Unremovable]. Apply Burn Immunity to self [Permanent, Unremovable]. Increase own Resistance to all attacks by 55% [Permanent, Unremovable].
Turn 1		Primordial Rune: Increase Quick Card effectiveness for all allies by 50% [Permanent, Unremovable].
Turn 2		Hero's Assistant: Increase Critical Strength for all allies by 50% [Permanent, Unremovable].
Turn 3		Magecraft of Louhi: Remove all Debuffs for all allies. Restore 2,000 HP each turn for all allies [Permanent, Unremovable].
Turn 4		Final Bombardment: Remove Surt Fenrir's [Ice Frosted Coating] passive.

Surt Fenrir
	HP	216,833
	LVL	90
	HP	239,420
	LVL	90
	HP	311,698
	LVL	90
	Class	Saber
	NP Bar
	NP Type	AoE
	Actions	Up to 3 per turn
	Traits	Humanoid, Male, Dragon, Heaven or Earth, Evil, Super Giant

Normal Attack		Normal attacks will hit AoE (all frontline party members).
Battle Start 1		Ice-Flame Body: - Apply Burn and Stun Immune to self [Permanent, Unremovable]. Increase ATK vs [Divine] trait targets by 50% [Permanent, Unremovable]. - 30% chance to apply the below effects to targets when normal attacking [Permanent, Unremovable]: -- Inflict Burn (500 damage per turn, 3 turns). -- Decrease Critical Star Drop Rate by 30% (3 turns).
Battle Start 2		Beast of the War Dead A+: Increase ATK vs [Divine] trait targets by 50% [Permanent, Unremovable].
Battle Start 3		Mental Debuff Immune: Apply Mental Debuff Immune [Permanent, Unremovable]
Battle Start 4		Frost Film: Apply Debuff Immune to self [Removed by Napoleon's field effect on Turn 4].
Break		Fire Shard of the End: Apply Nullify Buff to all enemies (3 turns) [Unremovable].
Break		Breath of the Ice Wolf: Apply Skill Seal to all enemies (3 turns).
Skill 1		Staff Destruction A++: Increase own ATK by 50% (1 turn). Decrease Debuff Resist for all enemies by 20% (3 turns). Increase Burn damage taken for all enemies by 100% (3 turns).
Skill 2		Giant's Outer Shell A: Apply Damage Cut to self by 1,000 Damage (3 turns). Recover 1,000 HP for self when attacked (3 turns).
Skill 3		Monstrous Strength B+++: Increase own ATK by 30% (2 turns).
NP		Lopt Laegjarn: Deal Damage to all enemies. Deal 200% Special ATK vs [Divine] trait enemies. Inflict Burn (1,000 dmg per turn) [Permanent].

Overview

Surtr Fenrir, the burner of the nine realms, looks to be a daunting enemy to face with his large frame and 3 HP bars, as well as his multitudes of buffs. Notably, he is immune to all debuffs until the 4th turn, and he retains an immunity towards mental debuffs even afterwards.
However, never fear! Support Sigurd is here with level 90, NP5, and 10/10/10 on his skills. He also comes with a 100% NP damage up, Burn Immunity, and 55% damage reduction and further support from various NPCs, which means that he’s . . . not that good?
While Sigurd’s NP hits really hard due to the buff, he starts off at 0% NP gauge, which means that it’ll take some time until he can unleash said NP. Time which he may not have, unless NP Charging supports are brought along. Outside of his NP, his normal hits are not too powerful, lacking class advantage, CE and stat from Fous.
Furthermore, he has the Divine trait, and guess what trait Surtr has a supereffective against? Despite the damage reduction buff, Sigurd ends up being less tanky than actual Archers, though the silver lining is that he is immune to Surtr’s burns.
As such, the best course of action is to ignore Sigurd and bring an Archer damage dealer of Chaldea’s own instead. Of course, this doesn’t mean that he is completely useless, which will be explained further down below.
Surtr’s normal attacks deal AoE damage, and though their individual damage isn’t that much, they are enough to exert long-term pressure with the help of his Burn effects (which can outpace the NPC heal-per-turn buff). Similarly, his NP can be tanked safely by higher-HP Archers (except for those with the Divine trait, to whom it deals 200% more damage), but it is generally wiser to put on an Evasion or Invincibility and avoid taking the damage altogether.
Aside from Burns, Surtr’s Breaks also apply rather annoying debuffs. The first Break has him apply an [unremovable] Buff Block on all frontline party members, while the second applies a Skill Seal, with both debuffs lasting for 3 turns each. This is where Sigurd’s targetable third skill comes into play, allowing him to protect the primary damage dealer (the Archer from Chaldea, not him) from incoming debuffs (Burns included) for one turn.
All in all, this fight ends up being more of a damage race to deplete Surtr’s massive health before his sustained damage ultimately wears down the Chaldean party. The boss’ low single-target damage, however, brings us to the last, most important point.
This fight can be soloed very easily by certain Archers.

Team Recommendations

The easiest and most effective option to beat Surtr is to have an Archer damage dealer solo him. Altria Pendragon (Archer), Chloe von Einzbern, and Asagami Fujino among others are capable of doing this.
Quick Archers also benefit from the stage’s Quick Performance Up, allowing options such as Attila the San(ta), Billy the Kid or Tristan to really shine.
Holy Shroud of Magdalene is recommended for soloing, as well as Maid in Halloween as the latter also increases the heal-per-turn buff provided by the stage (it is doubly excellent for Altria (Archer), who also has a powerful self-heal skill).
Atlas Academy Uniform is the recommended Mystic Code for soloing, providing emergency Invincibility, a counter to Surtr’s Skill Seal through its debuff clear (the Buff Block is unremovable), and its cooldown reduction increasing the solo Servant’s consistency.
Should one insist to fight the hard mode (i.e. using Sigurd as the primary damage dealer as the game intended), ample NP Charge and sustain support will be needed, as well as a secondary damage dealer (did you expect Sigurd to survive through the whole fight?). Servants such as Merlin, Zhuge Liang, or Hans Christian Andersen are powerful options to this end.

Video Links

Note that these videos are not affiliated with GamePress, but showcase some lineups that are effective in clearing the final challenge. These can serve as a good reference for how to rotate skills during this quest or simply to have a look at the encounter before diving in.