Druids' Repository

Whenever a creature you control attacks, put a charge counter on Druids' Repository.
Remove a charge counter from Druids' Repository: Add one mana of any color.

Derevi, Empyrial Tactician

Flying
When Derevi, Empyrial Tactician enters and whenever a creature you control deals combat damage to a player, you may tap or untap target permanent.
{1}{G}{W}{U}: Put Derevi onto the battlefield from the command zone.

City of Shadows

{T}, Exile a creature you control: Put a storage counter on City of Shadows.
{T}: Add {C} for each storage counter on City of Shadows.

Reconnaissance

{0}: Remove target attacking creature you control from combat and untap it. (If you activate during end of combat, the creature will untap after it deals combat damage.)

Emmara, Soul of the Accord

Whenever Emmara, Soul of the Accord becomes tapped, create a 1/1 white Soldier creature token with lifelink.

Master Biomancer

Each other creature you control enters with a number of additional +1/+1 counters on it equal to Master Biomancer's power and as a Mutant in addition to its other types.

Cathars' Crusade

Whenever a creature you control enters, put a +1/+1 counter on each creature you control.

Huatli, Radiant Champion

+1: Put a loyalty counter on Huatli, Radiant Champion for each creature you control.
−1: Target creature gets +X/+X until end of turn, where X is the number of creatures you control.
−8: You get an emblem with "Whenever a creature you control enters, you may draw a card."