I've noticed a glitch with both the Blue Warrior's Summon ability and the Red Barbarian's Fright ability (the one that allows him to deal 100% damage despite the enemies' color, not the Fright that puts out x2 tiles). In both cases, buying the ability multiple times reduces the cost of the ability but when I use the ability, it uses up an amount of mana equal to the full, non-reduced cost of the ability. I do not have this problem with the Purple Wizard's Cure ability, which is similar in costing.