Creature - Shade 0/1, B (1) Defender (This creature can't attack.) {B}: Slithering Shade gets +1/+1 until end of turn. Hellbent - Slithering Shade can attack as though it didn't have defender as long as you have no cards in hand.1
Illus. Daren Bader
It only checks if you have an empty hand at the time attackers are declared. If you get cards in hand after that, it stays an attacker. [Dissension FAQ 2006/04/13]