The Dragon Helm is a high ranked heavy armor helm in Final Fantasy XII that boosts the wearer's magickal defense by 41 (Zodiac) or 35 (original), HP by 70 and Strength by 9. Uniquely for a heavy armor helm, the Dragon Helm gives HP, usually a property reserved for light armor; although it gives less HP than the preceding Giant's Helmet, the Dragon Helm otherwise has better stats, and Strength is the biggest boon of heavy armor and so it is usually a good strategy to equip whatever gives the best Strength.
In the original PlayStation 2 version, the Dragon Helm is sold for 12,500 gil in Balfonheim Port after obtaining the Treaty-Blade, and is among the best purchasable helms and thus potential endgame equipment. It also rarely drops from Aeronite.
In the updated Zodiac versions, the Dragon Helm is not sold in normal shops but sells for for 6,250 gil. It is found as a treasure in Cerobi Steppe's North Liavell Hills (20% chance to appear, 50% chance for gil, 5% chance the item treasure is the Dragon Helm with the Diamond Armlet equipped) and Pharos - First Ascent's Wellspring Ravel - 1st Flight (always appears). It still rarely drops from the Aeronite.
Dragon Helm is a high level helm giving 41 or 35 Magick Resist depending on version, 70 HP and 9 Strength. Its stats make it a contender for endgame equipment; though its HP boost is not so great, any HP increase can be worthwhile and its other stats are good, though fall short of the top tier helms (Genji Helm, Magepower Shishak and Grand Helm). The strength bonuses make heavy armor ideal for frontline fighters, and the Dragon Helm is a good helm to equip over any inferior equipment the player may have on anyone who attacks physically, although a gun-wielder does not benefit from the strength-boost.
In the Zodiac versions, Uhlan, Knight, Time Battlemage, and Foebreaker can equip it natively, and the Red Battlemage can learn it if they unlock Exodus, the Archer can learn it if they unlock Shemhazai, and the Bushi can learn if they unlock Zodiark on their License Board. Dragon Helm is only useful to look for if the player has chosen these License Boards for the party. The player is most likely to obtain the Dragon Helm from Pharos in these versions, and so they will have Shemhazai from the story already, and Archer's unlock with it is among the better ones.
In The Zodiac Age versions, after fighting Belias the player can choose two License Boards per party member and so more characters can benefit from heavy armor, as it is usually a good idea to match jobs that use different types of armor to bolster light armor jobs' strength, and to give more durability to spellcasters.