Appa, Sky Bison

Flying, Trample
Loyal Companion — Whenever a creature you control attacks alone, you may tap Appa. If you do, that creature gains +3/+3 and indestructible until end of turn.
Sky Bison Stampede — 2W: Tap up to two target creatures your opponents control. Those creatures don’t untap during their controllers’ next untap step.
"Yip yip!"