Ok guys, this is really intriguing. I don't know if it's any good, but it's interesting for sure. 

First thing that comes to mind: target an exhausted unit you know you can kill. But is that really worth 1C1R + committing to a planet? Units in the warlord train are generally not that useful anyway. 

Possible good targets could be:

4 cost units in general, especially Front Line 'Ard Boyz

Captain Markis

Flash Gitz

Fire Warrior Elite

Fireblade Kais'Vre

Experimental Devilfish

VPs, RTs, Survivalists etc. (?)

I'm not a fan of this card, that said, here are my thoughts:

I can think of 3 triggers:

1. Battle at planet 1, you send your warlord to a different planet where this is deepstrike and use it to mop up one of the survivors

2. Battle at planet 1, opponent goes to this planet instead with warlord and you trigger to pull a threatening unit down the planet line.

In both of those situations opponent will need to win planet 1 with a unit remaining for it to trigger.  That makes bullet 2 a bit low in likelihood IMO.

3. Opponent unit is routed at a planet due to Terror or Ferrin or other ability (e.g ethereal) and you or opponent sent warlord to this planet.

Biggest drawback is that it must be triggered by a battle starting at planet and it is useless at planet 1 (unless you route further down line pre-battle) so you are gambling on unit being available in HQ post-trigger.  If opponent knows you are playing it becomes a red flag on your commit plans.  Also, for it to really have impact you need to destroy the unit in first combat round, otherwise they can just retreat again.

In terms of use:

1. Pick off trouble units (such as AOE units in terms of Kith)

2. Pick off elite groupies that protect elites from card effects (because you can't pull in an elite)

3. A more controlled set up of Holding Cell - you can effectively move a desired unit to the planet and pick it off.  As janky as holding cell is, i think this is the best use case for this card because it synchs with your own deck strategy (versus including the card as a possible response to opponent's deck)

4. Kugath to pull units into a planet so that they take damage from nurglings

5. Paired with defense battery

Difficult to use for these unless opponent triggers and thus unit stays alive at planet into next phases:

1. Warp Rift, Warpstorm or Turbulent Rift set up

2. Fetid Haze set up

Finally, doesn't seem much like an Eldar card.  Eldar wants units in HQ where they are exhausted the longest or set up for Doom.

Also possible to move a troublesome unit that just won on first planet like BAV to a planet far away to keep it out of sight. Only trouble is you gotta deal with it then.

It doesn't work when your opponents units are not in hq yet. So you need to trigger this after a battle has already taken place.

Seems like Urien style ;-)