Njal Stormcaller

I've had a bit to say about Njal, having used him for about half the games I've played with my Wolves.

Njal belongs in a Rhino with Grey Hunters, at the centre of your advance. The mobility afforded by a transport is important for making the most of Lord of Tempests, and you definitely want those fire points. His ability to cast two psychic powers means that you can always cast Storm Caller, which is a nice pseudo-KFF for mech armies. His 3+ to cancel psychic powers is the best anti-psychic ability in the game - 67% to cancel versus Runes of Warding's 50% chance to make the psyker fail at Ld10 - but of course doesn't increase perils chances like the runes do.

Njal is a useful character to take (specifically, instead of two rune priests, because their costs are similar) because he knows every psychic power, and there are a few Space Wolf psychic powers that are extremely situational but very good in those situations. If you, like me, dislike tailoring lists to fight certain opponents, that's really valuable, especially in tournaments. I played one game in a tourney where I was up against Chaos Daemons in Dawn of War where I won first turn, and was able to put Njal in the direct centre of the table and cast Tempest's Wrath, which ended up costing him an immobilised Soul Grinder, about five bloodletters, a wound on his Bloodthirster (battle report here).

Lord of Tempests is also amazing. By the time your opponent is getting ready to assault, you've a good chance to make everything within 24" difficult terrain to infantry, which messes with assault infantry royally, as you can imagine. In the late game Njal is literally shooting lightning without even thinking about it, which is especially great in Annihilation because you can rack up kill points without even trying.

Psychic powers and special rules aside, Njal is decent in combat but nothing to write home about, and he's not terribly durable with 2 wounds, a 3+ save, and no invulnerable. Essentially your strategy should be to keep him out of combat.