We currently have these Keywords in the game:

Armor: Prevents the first point of damage from each individual damage source.

Banner: Provides +1 Power to your Hero.

Guard: Units with guard prevent your Hero from being attacked.

Lifesteal: Damage dealt to the enemy hero by Units or Spells with Lifesteal gives your hero that much health.

Stealth: Units with Stealth cannot be attacked unless their Hero has been damaged this turn.

Wither: Damage dealt to Units (but not heroes) by Units or Spells with Wither will reduce both their health, and their Power.

More on Keywords in this blog post.

Did this answer your question?