Phase 1: Wiegraf (Human Form)
This is a 1-on-1 duel between Ramza and Wiegraf. Wiegraf is a powerful Knight with high speed and strong physical attacks. He uses 'Lightning Stab' and 'Holy Explosion'. Equip Ramza with the best available armor and a good weapon. A Monk secondary ability set (Punch Art) is highly effective for Ramza here, allowing him to heal himself with 'Chakra' and deal significant damage with 'Stigma Magic' or 'Wave Fist'. Alternatively, a 'Two Swords' setup with a strong weapon can also work. Focus on healing and hitting hard. Keep your HP high.
Phase 2: Velius (Lucavi Form)
After defeating Wiegraf, he transforms into the Lucavi demon Velius. This battle involves your full party. Velius has high HP, powerful area-of-effect attacks, and is accompanied by Archaic Demons. Velius is weak to Holy-elemental attacks. Prioritize eliminating the Archaic Demons first to reduce incoming damage. Spread your units out to avoid Velius's AoE attacks. Use 'Shell' and 'Protect' on your party. A Holy Knight (Agrias or Orlandeau) will shine here. Sustained damage and consistent healing are key.