Kaardas, Eager for Battle

Haste, berserk (This creature must attack)
Whenever another creature enters the battlefield under your control during a precombat main phase, put a berserk counter on it and it gains haste and berserk. Otherwise, put a defence counter on that creature. If you do, it has first strike and can't attack.
"But sir, the battle hasn't started yet"
-Lendos, Varuulian War Recruit