Re: Aegis Thousand Year War - DMM Online Game
@Tasogare: No, there's currently no other ways to reduce a unit's cost.
Most characters are fine at full cost; people have been doing difficult maps with a 13 cost Soldier Chief Katie. It's mainly a big deal when you reach the more difficult Challenge Quest maps, or if it's an event unit (i.e. Liana is probably going to cost 24 to deploy if you don't get any cost reductions for her). If the unit you have was a high-tier one you got from summoning, then you really don't have to worry that much. I've been playing just fine for the most part with a full-cost Platinum Witch Adelle, Princess Lilia, Valkyrie Dahlia*, and Black Archer Nanaly.
*After a year of playing, I got a second copy of her from base summoning, so she's my only platinum+ premium unit that has been cost-reduced.
The ones you really do want to cost-reduce are your silver units and gold units. Most silver units are easy enough to acquire, and they often reward players with gold units from Gold Rushes and Serial Codes, so it's quite possible to get those units at -1 or -2 cost just by playing the game normally. I only have 2 gold units (excluding Carrie) at -2 cost: Berenice and Iris. I got the 2nd reductions for these two in the last several months of playing.