+Momentum (3)
Tap target creature and put three stun counters on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)
Enchant creature
At the beginning of your upkeep, you may put a growth counter on Momentum.
Enchanted creature gets +1/+1 for each growth counter on Momentum.
Whenever Momentum Rumbler attacks, if it doesn't have first strike, put a first strike counter on it.
Whenever Momentum Rumbler attacks, if it has first strike, it gains double strike until end of turn.
Gatherer works better in the Companion app!