Oblivion is a Shadow Phantom creature with a difference - he possesses self awareness. He appeared at the climax of the battle to save Faerieland, rising from the ashes of the lesser wraiths.
You never learn...Prepare to fight!
Neopia will not survive.
The shadows slowly grow more repressive.
Embrace your fear.
Fear me and help me destroy everything.
Now that we are free, Neopia will not survive.
There will be nothing left when we are through...
Oblivion was always immune to one element (in fact, it healed him), and weak to another, but the elements rotated.