Board Thread:Questions and Answers/@comment-124.104.84.29-20150601023306/@comment-26021614-20150602000854

How to Obtain You can get two. As I mentioned, I rely heavily on boosting HP, so that the higher Max HP your unit has, the higher threshold you for Guardian Cloak's effect to start taking place. This works best using Double Kanon lead because the increase in defense makes it so that if your unit's HP is just above 35%, it can still withstand attacks from even the strongest bosses. Moreover, your unit cannot be poisoned or paralyzed, and not very many bosses have defense ignore or reflect damage, so you usually don't have to worry about those either.
 * Reward for clearing Band of Thieves and Undaunted Uprising in the Special Dungeon,Leon's Deception.

I said never because thus far, I have not needed it. I'm not saying I won't in the future but so far, no need.