The Holy Dragon only attacks with the Holy spell, which can be reflected; if the party is equipped with Reflect Rings, the battle becomes trivial. The Holy Dragon wastes turns casting Dispel to rid of the Reflect as well. Even though it only uses normal magic, it can be inflicted with Silence, rendering it immobilized. Although the Holy Dragon has no weakness, his HP is the lowest out of all the legendary dragons.
The Holy Dragon is one of the few bosses to appear on the Veldt and have a Rage. As such, the Holy Lance, obtained by defeating the Holy Dragon, is obtained in such a way as to prevent the player from stocking up on them. Players can still attempt to steal Holy Lances, but as it is a rare steal, it'll take a good amount of luck.
The revived Holy Dragon fought in Dragons' Den is a much more potent opponent. It counters most attacks by casting Curaga on itself, healing for 6000+ damage, and has Auto-Regen healing it even more. It has a chance to counter attacks with Heartless Angel, reducing the entire party to 1 HP. The Holy Dragon will attack several times a turn with Holy, Heavenly Wrath, a powerful physical attack, or Saintly Beam. Saintly Beam hits the entire party and cannot be reflected, so it has the potential to end the game instantly if used after Heartless Angel.
Only the Paladin's Shield, Cat-Ear Hood and Minerva Bustier provide protection from Holy-elemental damage, so bringing Terra, Celes, and/or Relm to the battle equipped with these armor pieces will provide much-needed protection. Another option is to bring Strago or Gogo to use the Force FieldLore. With luck or persistence, the Holy element will be negated, removing Holy and Saintly Beam as threats. From there, the player can cast Reflect on the Holy Dragon to neutralize its Curaga, and use non-elemental attacks that ignore Reflect while healing as needed from Heavenly Wrath and Heartless Angel. Reraise is recommended.
The sprite shared between Holy Dragon, Dragon, Red Dragon, and Great Dragon is virtually identical to the sprite found in some of the Thunderh class dragons in Bahamut Lagoon. Namely the Pontilac and General.
Along with the rest of the eight legendary dragons, there exists text within the game code indicating that Holy Dragon would summon one of the other dragons in battle to help fight the player. How this would be implemented is unknown; no actual coding for this feature exists.
On the Veldt, the Holy Dragon always appears right after the Behemoth King.