text: In some rare, strange cases, a planeswalker that is also a creature may block Thrasta while Thrasta is attacking that same planeswalker. (I did say strange.) Assuming no other creatures are blocking Thrasta and the blocking creature has no damage marked on it, Thrasta's controller must assign at least as much damage to that creature planeswalker equal to its toughness or the number of loyalty counters it has, whichever is greater.