An explanation of the strategy for the Archangel Santaquiel boss fight.
Use the lighter on Santaquiel to damage him. He is vulnerable after he moves. Santaquiel throws out gift boxes, which will explode in a + shape. Santaquiel will also say "Ho Ho Ho" and then throw the words at you. A sleigh will fly overhead, dropping ice shards. You can use the lighter to melt these. He will have snowflakes spinning around him after your first attack.
If Santaquiel is the boss of the fourth dungeon or later, there will be a second phase of the battle. In the second phase, continue using the lighter on him until he dies.