Moved to discussion from comments:

Awesome to see a summoner class. Was a lot of fun to play with.

Feedback:
IMHO the spinning fireball spell doesn't really fit the theme and is too strong and doesn't really fit the theme, though I understand the need for a ranged spell, was able to clear chambers and battlements with just that spell and no minions.

The minions get to be too strong as they scale with NG level. I took my friend's lvl 15 necromancer to NG+7 and the minions wouldn't die. And this was without using priest or paladin to heal them (which is great to see, perhaps they should be really hard if this combination is used). Lastly, it doesn't appear the bard's song affect them, which would be another cool interaction.