Ivan, I was obviously referring to Piece of Crystal SP summons, not SC Premium summons. The fact that they can earn stamp card rewards in increments and also be spent on refilling Stamina and Charisma should be enough to clue you in that I wasn't talking about them.

@anon, as long as you understand you're just giving yourself a placebo that's fine. If that feeling is worth enough to potentially hurt yourself in the long term then by all means, spend how you see fit. Also if you've already saved at least 300 Piece of Crystal then you've had ample opportunity to buy all the barracks upgrades which provide plenty of space for free players especially. Selling spirits is such a waste and I've never felt like I had too many spirits, if you start getting high you can always combine them with your Hashim fodder for bonus xp, even if you have no gold rarity units to raise its still better than outright selling them off.