I couldn't miss the chance to practice my drawing!
Divine Seal is a White Mage ability learned at level 15 and has a ten minute recast time. When used, the next spell the White Mage casts will heal double the normal amount. This will only effect healing spells, such as Cure and Curaga spells, and will not effect spells that Regenerate hit points, Drain hit points, nor does it effect the Raise spell. If the next spell cast is not a Cure spell, the ability is wasted and has no effect.
In A Realm Reborn and Heavensward, Divine Seal appeared as a White Mage ability available after completing the "O Brother, Where Art Thou" level 40 job quest. It increased the potency of healing magic by 30% for 15 seconds, and had a 60 second recast time.
Due to the development team's desires to remove duplicate abilities for the Stormblood expansion, Divine Seal was replaced with the new cross-role ability Largesse, which is available to all healer jobs.