Defense Node, also known as Defender or DefenseSys, is an enemy from Final Fantasy IV that appears alongside CPU and Attack Node in the Tower of Babil. It will often heal the CPU for 2,000 damage, severely hampering the party's efforts to defeat it.
In the Nintendo DS version, the Attack Node poses a large threat with its Laser Barrage attack. The Defense Node should be the last one to be defeated. Also, in this version the Defense Node absorbs nearly all elemental damage. Rydia should use Titan once the CPU and Attack Node are destroyed, as none of her other attacks at this point will be effective.