ED-E, Lonesome Eyebot

Flying
ED-E My Love — Whenever you attack, if the number of attacking creatures is greater than the number of quest counters on ED-E, Lonesome Eyebot, put a quest counter on it.
{2}, Sacrifice ED-E: Draw a card, then draw an additional card for each quest counter on ED-E.

Fallout

If the number of attacking creatures isn’t greater than the number of quest counters on ED-E when you attack, its second ability won’t trigger at all. When the ability tries to resolve, if the number of attacking creatures is no longer greater than the number of quest counters on ED-E, it won’t resolve, and you won’t put a quest counter on ED-E.