That seems quite complicated.
- By "next turn only" do you mean "next turn only for each use" or "next turn only, once-per-battle-only"? EDIT: Source point requirement, so that's pretty much only a once-per-battle thing.
- What's to stop that character from using his new first-turn initiative and sudden 6 AP to instead attack any enemy he feels like and killing them instead of the target enemy? If nothing, then it doesn't seem like this needs to target an enemy at all, but move the user to before any enemies move (since everyone will use this to move before the fastest enemy in range).
- If a fighter is using this ability, it already implies that most enemies in the turn move before his allies, and many may have already moved. So how likely is it that an enemy will be able to use their own Interdect to cancel the fighters, since if he's using it, he's likely moving after the enemies have already acted in that turn.
- The shield requirement seems to serve no function except to ensure that the fighter has to spend 2 AP to do weak attacks.
