Soul of Innistrad
All four are extremely solid out of the box - each one built to a clear gameplan, with almost no obvious cards you should cut
-3 Make an artifact token with "If a source would deal damage to you, prevent 1 of that damage." This is a nod to an ability on the card Urza's Armor
And finally, we have Basal Sliver, Enduring Renewal, and Changeling Outcast on top of our changeling trio for an infinite storm count, infinite black mana, and infinite ETB triggers
While it doesnt have the same explosive potential, just getting a card back when it deals combat damage to a player or planeswalker means that this card is stronger in the late game
When you exile a card this way, target creature you control gets +X/+0 until end of turn, where X is that card's mana value