Thank you! Yeah, the Siren can't create water on an occupied space. I should probably change that (since the space is turned into water anyway if an adjacent one is targeted. I believe I must also change the way skills are targeted in general, because as of right now, some are too obtuse to pull off (case in point, the siren's wave ability).
As of right now, the "AI" just looks for enemies in range and attacks. If none are found, it moves each character to a random spot, favouring raised terrain. So yeah, I need to figure that one out.
Good idea on the gold thing! I'll probably manage to put it in the next version.