Quote Originally Posted by MalusCorvus View Post
Should have asked this sooner, but alas... I have Ayami, and I intend to use her. For combat, of course. :P

But I have three of her, and while the other two would be great for XP and lowering her cost, should I fuse them both at once or individually? Is the cost decrease per unit, or is there a fixed chance per fusion assuming a duplicate is involved?
fusing them both at once or individually doesnt not change your chances.
http://millenniumwaraigis.wikia.com/...it_Combination
scroll down to see % chances for CR and SU

some people keep them around while waiting for fairies to combine (since plat rarity units give good exp), while some dont care and just feed, and some look at the unit's level before feeding (because lvl 40+ consumes a lot of gold otherwise if you don't use high exp combinations to reduce the amt of gold spent)
but in the end, it doesn't matter that much and is largely a personal preference.