Shatterskull Attacker 1RR
Creature - Giant Warrior (Rare)
If Shatterskull Attacker was kicked, it enters the battlefield with a +1/+1 counter on it.
At beginning of your end step, return Shatterskull Attacker to its owner's hand unless it has a +1/+1 counter on it.
Kor Celebrant 2W
Creature - Kor Cleric (Common)
Whenever Kor Celebrant or another creature enters the battlefield under your control, you gain 1 life.
Nimana Skydancer 2B
Creature - Human Rogue (Common)
When Nimana Skydancer enters the battlefield, target opponent mills two cards.
Tazeem Roilmage 1U
Creature - Merfolk Wizard (Common)
When Tazeem Roilmage enters the battlefield, if it was kicked, return target instant or sorcery card from your graveyard to your hand.
Ignoring the 1/4 Soul Sister, another mill Rogue, and party Archaeomancer, Shatterskull Attacker might be something you can't care less to cast not-kicked early game.
So... curve Metallic Mimic or Bramblewood Paragon into that Shatterskull fella for a hasty 5/4 on Turn 3 that sticks around? Not too shabby, probably not good enough for Modern but given enough Warrior support could be a thing in Pioneer, even though obviously you can't play the Paragon there.
The other 3 are barely worth mentioning. The Cleric might be decent sideboard material but other than that it's all Limited fodder, and boring ones at that.