Fire

Primary Eidolon : Crow Kulwach (eidolon from fire raid. 40% fire atk, 20% hp up. Information come from japan wiki so let me know if i'm wrong)
Friend's Eidolon : Apocalypse to gain some survival rate with blind, Crow Kulwach for more hp or Typhon for instant atk buff during union burst time.

Gawain + sniper shot : 40% Def debuff, 20% atk debuff, 15% A frame atk buff. Not legendary but definitely worth it (thx Wanderer for the tip)

Amon : For her affliction immunity. And because she is free...
Agni : +10% fire atk buff, a C frame self atk buff (10 to 80% based on hp lost) And because she isnt trash
Brynhildr : heal 1200 hp every 6 turn. 10% A frame atk buff + Double attack rate increase
Baphomet : 10% A frame atk debuff

Damage oriented team. 40% def debuff, 30% atk debuff, no damage mitigation at all.
Brynhildr's buff will be used during auto atk, 3 turn double attack rate will help to increase burst gauge faster. Agni's assist skill will also help with her double attack rate when atk buffed.
A lot of damage ability available when damage spike is needed. Agni + Gawain's buff will be used together for burst or whenever sustained damage is needed.
Amon devil's kiss will help to prevent some annoying debuff (who said Medusa?)
Main weapon should be SR sword from Typhon's event.