Bran Redmaw
Bran Redmaw Wolf Lord of the Bloodmaws Great Company of Space Wolves, Bran is cursed with the Wulfen and is known to occasionaly turn into a big werewolf in battle. He is the Space Wolves Commander in Forgeworld's Doom of Mymeara Book. The book covers an Eldar invasion of an Imperial Ice World and the Space Wolves coming to save the day again. He is also mentioned as taking part in Games Workshop's new campaign book which features Space Wolves, Dark Angels, Grey Knights and Chaos Daemons.
Tabletop
Redmaw is another of those very expensive 200+ point characters, but pound for pound is probably high value for what you pay for.
He's got your regular Wolf Lord statline and all your traditional rules and gear.
What he gets on top of that is a S+1 AP2 shredding axe that strikes at initiative. So he's pretty handy in a scrap. Though the axe alone does not justify his points cost.
Each turn after the first he rolls a die, adding +1 for each unit in combat that he can see. If the result is a 5+ he goes full Werewolf and powers up to near-Primarch levels; gaining WS7 S/T6 I6 A5. As well as Eternal Warrior, Fleet, Furious Charge, Feel No Pain, Fearless, as well as Rending close combat attacks. However he does lose the axe and any ability to shoot, but he does keep all of his remaining gear, so he still has his 2+/4++ saves and sticks with whatever squad he was attached to.