Allies and champions may have keywords that give them special abilities, such as the mentioned Braum regeneration. To see what these abilities do, you can always right-click the card and hover over the keyword to get a quick explanation of the tooltip that pops up.
Here’s a list of them:
Last Breath: When this unit dies, it causes an effect.
Support: Gives effect to the unit to the right of this ally when it attacks.
Lifesteal: The damage caused by this unit heals your connection to 20.
Overwhelm: Extra damage to blockers is transferred to enemy communications.
Elusive: Can only be blocked by another elusive warband.
Nexus Strike: Get a certain effect when hitting an enemy Nexus.
Regeneration: Treats lost health at the beginning of a round.
Challenger: You can choose which unit is blocking this opponent when he attacks.
Strike: Gives a certain effect when an enemy unit attacks.
Can’t Block: Can’t block an enemy unit from attacking.
Frostbite: unit attacks become zero.
Tough: Get one less damage from all sources.
Enlightened: Causes effect when reaching mana ten.
Ephemeral: This unit dies after an attack or at the end of a round.
Fearsome: Cannot be blocked except by enemies with three or more attacks.
Double Attack: It attacks twice, but cannot defend itself.
Barrier: Cancels damage once.
Quick Attack: Deals the first attack blow, dealing damage and potentially killing an opponent’s ally before they can retaliate.
Play: Launches a linked effect the first time a map is played.
Stun: This prevents you from using an ally to attack or block a round.
Recall: It causes a tied effect when a card returns to your hand.
Stop: This will undo the spell.
Lifesteal: This treats Nexus by the specified amount.