Arsenal Halphas is Beast I class, so Cavalry class Servants are best for dealing damage, while Avenger class Servants can survive for longer than other classes. Try to avoid bringing Knight class Servants. In summary:
- Knight class Servants (Saber, Lancer, Archer) are weak to its attacks and deal neutral damage.
- Cavalry class Servants (Rider, Caster, Assassin) receive neutral damage from its attacks and deal double damage.
- Berserker class Servants are weak to its attacks and also deal +50% damage.
- Ruler class Servants receive neutral damage from its attacks and deal neutral damage.
- Avenger class Servants resist its attacks and deal neutral damage.