Vigilance
The Defender's primary focus is to protect the team. When his allies are in danger, the Defender is able to look deep within him or herself and rise to the occasion.
As a defender you pay one less Magic point for each buff or heal you give to teammates while in combat. You pay the normal cost out of combat and to buff/heal yourself.
Build
Defenders are a diverse bunch, but tend to use Sorcery skill and Sorcery schticks, prefering any power that lets them use their special ability.