Illusionary Wall

Defender, flying, first strike
Cumulative upkeep (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

"Let them see what is not there and feel what does not touch them. When they no longer trust their senses, that is the time to strike." —Gerda Äagesdotter, Archmage of the Unseen