A variant of the Wraithguard that 6E introduced into the sprues are the Wraithblades (also known as Klaivaulch, but Eldar don't openly call them that because Khaine would unleash his wrath on them), a type of more kill-hungry Wraithguard with big helm crests that don't compensate for anything at all with their Ghostaxes or Ghostswords. In fact, the Wraithblades are so angry that their simmering rage is nearly as great as that of Angry Marines. So much so, in fact, that Seers need to isolate them from other Wraith Constructs or else they would be infected by rage (like that one G1 Transformers episode that introduces the Hate Plague). Not to mention that their Spirit Stones actually burn when activated.
It is unknown what makes the Wraithblades so damned angry, although some theories might suggest that Khaine might have something to do with it...or its just Eldrad being the dick as usual. Whatever is the case, they are known to cause even Khorne affiliated armies a severe case of critical existence failures. One must just wonder what it would be like if Khornates actually subdue one and got a hands on its pissed off Spirit Stones. Extra Heresy maybe? Think about that for a moment, a stone with a soul that would otherwise feed Slaanesh and is instead making the god of violence proud sounds like a crazy attempt to escape a /d/evious fate.
In a way, they behave like Chaos Dreadnoughts, who go insane without someone to cut up. It's just that they get treated a little better by not being ripped out of their shells and being subjected to pointless torture. Instead of guns, they carry around either a pair of Ghost Swords or a Ghost Axe and Force Shield.
Dawn of War III
In Dawn of War III, Wraithblades are elite CQC units designed to rip apart infantry and vehicles like cotton candy. They are one of the most 'must-have' units for the Eldar due to the combination of its relatively high health, strong resistance, surprising bursts of speed without the need of a Warlock and relatively high damage for what they cost in relation to their commonality.
Suffice to say, Wraithblades are quickly getting a reputation if you do not have the necessary means to defeat them (Hint, it involves Lascannons and other anti-armor weapons). However, they are still slow (Even if DOW3 intentionally made them faster for some reason) and can't be taken out by hero units with their bullshit special abilities.
On the Tabletop
Wraithblades come in two flavors; the offensively oriented Ghost Swords or the defensively geared Ghost Axe variants. As both loadouts cost the same right now, it's entirely dealer's choice on what they enter the fray with. Ghost Sword Wraithblades get one more attack per model than the axes do and, unlike the axe, get to make each attack at the full 3+ WS Wraith units typically have. Ghost Axe Wraithblades are slightly clumsier and will only hit on a 4+ without psyker support, but each hit potentially does more damage (d3 wounds a smack) and unlike their dual-wielding cousins, Ghost Axe wraithblades get to enjoy a 4++ invulnerable save courtesy of their Force Shields. Regardless of their loadout, a Wave Serpent is effectively mandatory for these guys: at a plodding 5" base movement speed with absolutely no ranged presence, Wraithblades are extremely vulnerable to getting focused down while they slowly shuffle across the board. If properly supported, your Wraithblades are simultaneously your most durable and most lethal infantry available to you. However, that support comes at a premium and you're already paying a fairly steep price per Wraithblade in your army. If you invest in Wraithblades, you need to pay very close attention to them if you want them to earn their points back.