I guess the slots are the "random" way to level up or get special attacks or whatever. It is a little weird. I just started playing too and I'm only about an hour or so in. So far I'm liking it, but it's very linear and there are too many cut scenes. Does the world open up where you can just wander around and explore eventually? Even though some people feel it's too button-mashy, I like the combat system. You still get to position yourself, block, and evade in what feels like real-time rather than turn-based.