Lim-Dûl's Paladin

Trample
At the beginning of your upkeep, you may discard a card. If you don't, sacrifice Lim-Dûl's Paladin and draw a card.
Whenever Lim-Dûl's Paladin becomes blocked, it gets +6/+3 until end of turn.
Whenever Lim-Dûl's Paladin attacks and isn't blocked, it assigns no combat damage this turn and defending player loses 4 life.