Megatog

Sacrifice an artifact: Megatog gets +3/+3 and gains trample until end of turn.

Atog

Sacrifice an artifact: Atog gets +2/+2 until end of turn.

Enduring Renewal

Play with your hand revealed.
If you would draw a card, reveal the top card of your library instead. If it's a creature card, put it into your graveyard. Otherwise, draw a card.
Whenever a creature is put into your graveyard from the battlefield, return it to your hand.

Krark-Clan Ogre

{R}, Sacrifice an artifact: Target creature can't block this turn.