Muireann, the Braveblade

Vanguard (Whenever this creature attacks for the first
time each turn, after this phase, there is an additional
combat phase.)
Whenever Muireann, the Braveblade attacks,
it gets +X/+0 until end of turn, where X is
the number of attacking creatures you control.
Battalion -- Whenever Muireann, and at least two
other creatures attack, Muireann deals 3 damage to any target and you gain 3 life.