Ball Lightning
Creature — Elemental
Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Haste (This creature can attack and 
as soon as it comes under your control.)
At the beginning of the end step, sacrifice this creature.
The most frightening storms are those not woven by nature's hand.
6/1
Illustrated by
Foundations#618RareEnglishLegality
Rulings
Feb 1, 2007
The creature is sacrificed at the end of every turn in which it is on the battlefield. There is no choice about what turn to sacrifice it.