Ageless Sentinels

Oracle Text

Defender (This creature can't attack.)

Flying

When Ageless Sentinels blocks, it becomes a Bird Giant, and it loses defender. (It's no longer a Wall. This effect lasts indefinitely.)

Card Rulings

10/4/2004 It becomes both creature type Giant and creature type Bird.
8/1/2005 Once it stops being a Wall, it can attack because it also loses Defender.