Lord Tirian said:Fun thing about them: As they're not solo monsters, you can add weaker versions of the PCs as time duplicates. Even more fun: The phane gets a heap of flavour, if it isn't killed on 0 hp, but instead vanishes, just to re-appear later. If one stops to think that flavourful abilities have to be anchored in the statblock, it's easy to "script" fun scenes. 4E already focuses on more linked encounters - a second phane arriving mid-battle (representing a time-stream duplicate) is basically made for the system.
You know, I have an idea for this encounter. A couple of adventures before this encounter, tell the party members that had a strange dream where they fought themselves. Give a generic description of the battle and perhaps feature a major magical item you plan to give them.
Then when you fight the Phane, he summons up duplicates of the party as they were a few levels ago. If the PC's don't get the hint and still use lethal damage and kill one of their doubles, you can take the character sheet away and force them to go back to where they were a couple of level ago to retrieve the body. Time paradoxes are fun.
Not something I'd want to see in official rules mind you, but a DM could have a lot of fun creating that ability and building an encounter around it.