These are the spell steps:
- Cleanse the target
- Create 8 Skulls.
- Give the target Magic+2 Attack.
- Deal 1 normal damage to the target (supposedly to remove barrier)
- Deal Magic+2 true damage to the target
- Barrier the target.
That means 2 things: the attack is gained first and independently of life lost, and barrier will not save you from the true damage.