Using the Skull of Corruption it is possible to create a permanent clone of yourself. Clones usually disappear after the 30 second time limit but there is a way to make a clone of yourself last forever.
1. Go to a cave that you do not mind never entering again with the Skull. This cave should have an NPC near the start. Capstone Cave, west of Bruma is ideal.
2. Kill all NPCs in the cave except for the NPC at the start. The NPC at the start should not detect you as you do this. 100% Chameleon or Invisibility is greatly helpful.
3. Move all the dropped weapons into containers, onto the bodies, or just hang on to them.
4. Drop the Skull by the NPC at the start and initiate combat.
5. Disarm or disintegrate his/hers weapon. Having no other choice, he/she should pick up the Skull and blast you with it. (If the NPC is casting spells at you rather than picking up the Skull, simply Silence him/her.)
6. Kill the NPC quickly.
7. Pick up and drop the Skull. The reason for this is to ensure that the skull does not get cleared out when the cave respawns.
8. Run out of the cave. Your clone should follow you out. When he does, he will be permanent until you re-enter the cave.
Because you cannot re-enter the cave, you cannot have your clone and the Skull of Corruption at the same time.
You are free to kill your clone and his body will not disappear. This makes him the ideal warrior to lead around with the Staff of Worms.
If you want to loot your clone, simply save and reload in the same area as him.
There is another method if you have access to an alter of spellmaking and have high level Mysticism.
1. Create a spell that has 100% Reflect Spell on touch.
2. Go to a cave with a killable follower.
3. Clear out the cave and move all weapons to the dead bodies.
4. Tell your follower to wait as far as he/she can from the door while still keeping it in sight.
5. Cast your reflect spell on him/her.
6. Back up to the door and fire the Skull of Corruption at him/her.
7. Drop the Skull of Corruption before the blast hits your follower.
8. Kill your follower.
9. Run out of the cave before the Corruption effect wears off.