Mightstone

Flying (This creature can't be blocked except by creatures with flying or reach.) First strike (This creature deals combat damage before creatures without first strike.) At the beginning of your upkeep, you may sacrifice an artifact. If you don't, tap this creature and it deals 2 damage to you.

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.) This creature doesn't untap during your untap step. 9: Untap this creature. Activate only during your upkeep.

2: This creature gets +1/+0 until end of turn.

T, Sacrifice an artifact: Put a +1/+1 counter on target creature. Activate only during your upkeep.

Destroy all artifacts. They can't be regenerated.

2: Prevent the next 1 damage that would be dealt to any target this turn. Return this artifact to its owner's hand at the beginning of the next end step.

2, T: Target player mills two cards.

Players can't untap more than one artifact during their untap steps.