Concentrate

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on Ajani's Pridemate.

When Kor Hookmaster enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Enchant nonland permanent
Enchanted permanent can't attack or block, and its activated abilities can't be activated.

Return up to two target creatures to their owners' hands.

Tranquil Cove enters tapped.
When Tranquil Cove enters, you gain 1 life.
{T}: Add {W} or {U}.

Dauntless River Marshal gets +1/+1 as long as you control an Island.
{3}{U}: Tap target creature.

Destroy target artifact or enchantment. You gain 4 life.

Return target nonland permanent to its owner's hand.

Flying
When Resolute Archangel enters, if your life total is less than your starting life total, it becomes equal to your starting life total.

When Frost Lynx enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Defender (This creature can't attack.)
{3}: Until end of turn, Gargoyle Sentinel loses defender and gains flying.

Enchant creature
Enchanted creature gets +2/+2 and has vigilance. (Attacking doesn't cause it to tap.)

Whenever you cast a white spell or a Plains you control enters, you gain 1 life.

Flying
When Tower Geist enters, look at the top two cards of your library. Put one of them into your hand and the other into your graveyard.