Only four themes? Really?
The main attraction to this theme is the beast companion you get, which can be a blink dog, displacer beast, fey panther, or owlbear, all of which seem pretty strong for what is in all honesty an optional option.
Yeah they only have half your usual hit points as a cap, but—for example—allies adjacent to a displacer beast gain a +1 power bonus to all defenses, while those next to a blink dog can teleport to another square next to it as a move action. In addition the level 5 and 10 features let you have combat advantage against any enemy next to your companion, and communicate normally with it and similar enemies respectively. Like spirit companions if they die you burn a healing surge and can just conjure it again from the Feywild as a minor action (though if you wait for a rest it comes back with full hit points).
The powers let you heal them for free, use a move action to send it back to the Feywild, and transform into whatever your companion is. None seem particulary neat; though safe banishment is an at-will, it takes a move action to remove and re-summon it. I think making it an immediate interrupt-encounter to save it (and a healing surge) would have been a lot better and more thematic. On a similar vein, companion form gives you your companion’s aura, but the use of any power ends the effect. Kind of meh.
Anyway, I guess the balancing act is that their defenses are rather tame (13-15 to start with), making them tempting and frail targets. Oh well, the only player I expect to pick this up is Randy, and that is just to have an owlbear companion as part of an inside joke from a previous campaign.