"Put a minotaur at the head of an army and suddenly all the soldiers act like they have horns."
—Gideon Jura

Ondu Champion

Rally — Whenever Ondu Champion or another Ally you control enters, creatures you control gain trample until end of turn.

The List

Battle for Zendikar

Rally — Whenever Ondu Champion or another Ally enters the battlefield under your control, creatures you control gain trample until end of turn.

If a creature with a rally ability enters the battlefield under your control at the same time as other Allies, that ability will trigger once for each of those creatures and once for the creature with the ability itself.

When an Ally enters the battlefield under your control, each rally ability of the permanents you control will trigger. You can put them on the stack in any order. The last ability you put on the stack will be the first one to resolve.