As with Erim, hit the light weakness with Maxim's Dual blade, Arty's Zap, or Selan's Holy whip or Super sword
Uses Terror wave on turn 1 and every 6 turns after. It's a non-elemental attack on the whole party (power 600) with a 20% chance each of confusion, poison, and sleep, so cure them all at once with Revival sleep on Arty's Silver robe.
Maxim can prevent poison with the Pearl armor and confusion with the Pearl helmet. Other party members can prevent confusion with the Ghostclothes and sleep with the S-myst ring.
Uses Dark reflector on turn 4 and every 6 turns after. It then lasts until attacks or status ailments aimed at Daos have been reflected 3 times, and it doesn't wear off over turns. Save strong IP skills and spells until its reflections run out.
On other turns, it repeats this order: Dark fry (darkness, power 800 on the whole party) → normal attack → Thunder → Firebird → Ice Valk → Dragon → normal attack. To match the next attack, use the IP skills on the Gold gloves to reduce fire, the Plati shield (Maxim, Guy) for ice, the Plati gloves (Selan, Arty) for thunder, and the Rune gloves (Arty) for darkness (user only)
If things start to fall apart, use the IP skill Phoenix on Maxim's Pearl armor to revive all fallen party members and fully restore everyone's HP and MP