Flying, Warcry, Bond
Entomb: You gain 3 Armor.
Entomb - The ability of a unit with Entomb will activate when it dies. This combines well with effects that sacrifice units as a cost.
Flying - Flying units can only be blocked by other flying units, but can block ground units normally. They can also be directly attacked by Killer units and Relic Weapons.
Warcry - Each time a unit or Relic Weapon with Warcry attacks, it grants a permanent bonus to the top-most unit or weapon in your deck. Even if it's a few cards down, you'll get to stack up the bonuses on it over multiple turns.
Bond - When played, you may exhaust another unit of the same type to reduce this card’s cost by the exhausted unit’s strength.