Dramatist's Puppet

When Dramatist's Puppet enters, for each kind of counter on target permanent, put another counter of that kind on it or remove one from it.

Geralf's Mindcrusher

When Geralf's Mindcrusher enters, target player mills five cards.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Nimbleclaw Adept

Bigby's Hand — {T}: Untap two other target permanents. Activate only as a sorcery and only once each turn.

Myojin of Cryptic Dreams

Myojin of Cryptic Dreams enters with an indestructible counter on it if you cast it from your hand.
Remove an indestructible counter from Myojin of Cryptic Dreams: Copy target permanent spell you control three times. (The copies become tokens.)

Tribute Mage

When Tribute Mage enters, you may search your library for an artifact card with mana value 2, reveal that card, put it into your hand, then shuffle.

Corridor Monitor

When Corridor Monitor enters, untap target artifact or creature you control.

River Kelpie

Whenever River Kelpie or another permanent enters from a graveyard, draw a card.
Whenever a player casts a spell from a graveyard, draw a card.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Wingspan Mentor

When Wingspan Mentor enters, put a flying counter on target non-Human creature you control.
{2}{U}, {T}: Put a +1/+1 counter on each creature you control with flying.

Thopter Mechanic

Whenever you draw your second card each turn, put a +1/+1 counter on Thopter Mechanic.
When Thopter Mechanic dies, create a 1/1 colorless Thopter artifact creature token with flying.