Quote Originally Posted by Xeare204 View Post
Most notably I'm curious about Platinum Armors. Are they best used on platinum units then?
A platinum armor isn't a type of fairy, he's just a blob of experience.
When used with three fairies with x2 modifiers (so black fairies for black units, gold fairies for gold units) nets 8,000 EXP

So it doesn't matter who you use the Platinum armor on, but it does matter which fairy you use, if it matches your unit's rarity.