Riven, Exiled Blade

When Riven enters, create Runic Blade, a legendary equipment token with "Equipped creature gets +1/+1",
"{2}: Equipped creature gains +3/+3 and lifelink until end of turn, destroy this equipment.", and "equip {2}, equip warrior {0}".

If Riven is the only creature you control, she gains +3/+3 and menace.

If Riven is put into exile from anywhere, return her to the battlefield at the beginning of the next end step.