Esper Sentinel

Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays {X}, where X is this creature's power.

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Baylen, the Haymaker

Tap two untapped tokens you control: Add one mana of any color.
Tap three untapped tokens you control: Draw a card.
Tap four untapped tokens you control: Put three +1/+1 counters on Baylen. It gains trample until end of turn.

Warren Warleader

Offspring {2} (You may pay an additional {2} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Whenever you attack, choose one —
• Create a 1/1 white Rabbit creature token that's tapped and attacking.
• Attacking creatures you control get +1/+1 until end of turn.