Just a couple very minor suggestions from me.
* Cloak of Night ---> Rename to Cloak of Obscurity or Cloak of Gloom(anything) to avoid confusion about the item "Cloak of Night".
* Skeletal Knight: (Cooldown on re-summoning changed to 20 seconds. No summon cost.) ---> Move to Core 1.
Tier 1
* Skeletal Knight Training: Skeletal Knight receives a 5/10/15% enhancement bonus to maximum hit points. (or some other form of defensive stat to keep it from instantly dying)