Wraithlords are towering wraithbone constructs imbued with the spirits of dead Eldar warriors. They're bigger than the human-sized Wraithguard, and instead of carrying guns that rip holes in space-time, they're either carrying heavy weapons on their shoulders (like a big-ass rifle) or huge fucking swords.
The one pictured has has all the heavy weapons it could fit on its shoulders AND the huge fucking sword,
which is not strictly legal under 40k rules it is now thanks to Saint Kelly, but there are a couple of things to note in this regard:
1) Purely in fluff terms, finding a dead Exarch in the Infinity Circuit takes a Warlock or specialist Farseer, so the very notion of talking the Exarch into a wraithbone shell with no dick is setting a pretty high bar in the first place.
2) But suppose you achieve this. The Exarch's in the Wraithlord, and now the whole thing comes to life, and starts grunting "Diiiiick! Where's my diiiick?" and heads straight over to the nearest shelf of space-hairdresser weapons, and sticking too many giant anti-tank weapons on its shoulders, AND a huge fucking sword. You, the bastard psyker who incarcerated the poor fella in there is hardly likely to start arguing with it about 40k game load-out limits, now are you?
3) I think not, no. You'd be checking your runes, and pointing the thing in the direction of the nearest Dreadnought with a certain malicious glee in your psychic heart, wouldn't you. And I can tell you for nothing, that in game terms, it's worth the time spent dicking around with magnets just to see the look on your opponent's face!
Wraithlords aren't quite as dominant as Space Marine Dreadnoughts, partially because they don't have two power fists since 4th edition.
Except they are. One Wraithlord punch that penetrates armor can blow up a poor Dreadnought, whereas a Wraithlord can take 3 solid power fists before keeling over.
Also because they're usually whining about not having dicks anymore, behavior Idranel objects to. And very much because they defy tactical best practice rather more often than they should, attempting to use their giant fucking swords to slice the dicks off opposing Dreadnoughts.