Lone Aurochs

Haste, Vigilance
Whenever Lone Aurochs attacks, it gets +1/+0 until end of turn for each other attacking Aurochs.
Whenever a creature you control dies, add {r}{g}, it doesn't empty from your mana pool until end of turn.
{t}, Sacrifice a creature: Look at the top X cards of your library, where X is its power. Put a creature from among them into your hand, then shuffle your library.