Canoptek Wraith
Canoptek Wraiths are automated Necron constructs that, like the Canoptek Spyder, oversee maintenance and repairs over all things Necrons so when the time comes to set off the alarm clock, the Crons would be all up and ready to break some spines. However, they also act like a first line security protocol robot, serving as the eyes and ears of the central operating system of any Tomb World, patrolling for intruders and swiftly dealing with them.
Overview
Its primary tool is its Phase Shifter, a Dimensional Destabilization Matrix that allows a Wraith to phase in and out of sync with the normal space-time continuum much like a C'tan Phase Blade. Though the primary purpose of this device is to allow a Canoptek Wraith to reach into and repair solid machinery, it is equally effective when used to deal with intruders who have breached the protections of a subterranean Necron stasis facility. In such a case, a Canoptek Wraith can phase its claws and tendrils inside an opponent, and resolidify them to sever arteries, nerve clusters and other vital pathways without leaving an external mark of what caused the victim's death.
Despite their similarities in function, Canoptek Wraiths are lower in class to that of the Canoptek Spyder, their relationship is thus, similiar to that of a Techpriest and Servitor of the Adeptus Mechanicus. As they are primary probe mechanoids, the Wraiths are programmed to report back to their Canoptek Spyder controllers via an interstitial interface rather than act under their own direction.
They used to look like a modified Necron Warrior like the Necron Destroyer and Flayed Ones but with the lower torso replaced with a snake-like tail and their hands turning into razor-sharp talons. The original fluff dictated that they were the Necron's chief close combat specialists (Flayed Ones notwithstanding) and it has been suggested by certain Imperial savants that in ancient days before the War in Heaven, that Wraiths were once Necrontyr murderers and psychopaths before their eternal entombment within their cold, metallic husks. Nowadays they have been given a face lift and now count as a Necron Construct, not a troop. And as you may already know they are much spookier now, despite being less skeletal.
The older design, as of 9th Edition, seems to be repurposed into Ophydian Destroyers.
Canoptek Crunch
These are some scary snake mother fuckers. They used to be the Grilled Cheese Sandwich of the Necron Codex, possessing a very swift 12" movement and an infuriating 3+ invulnerable save. This made them absolutely enraging to fight, way harder to kill than they had the right to while they could just Wraith Form through everything the moment they started feeling the heat. And if you downed one, there's a chance it could just self repair and get right back up.
9th Edition didn't significantly buff or nerf them, but did knock down that aspect of them by bumping the invulnerable save to a 4+. Thank god. In addition to this, their strength lost 2 pips (which was compensated for in the main weapon profile) while they gained an extra attack and a pip of save. With T5 3W Sv3+ and the aformentioned InvSv4+, they are still a monster to shift.
When it comes to dealing damage, the Wraith are still pretty customizable. By default, they come with a melee-only set of weapons, featuring S6 AP-2 2d Vicious Claws or the double-attacks S4 AP-1 1d Whip Coils. A classic elite vs. chaff clearing set of profiles, but still a welcome one.
As with its similarly built heavy version, the Canoptek Spyder, all ranged weapons are optional. The two on offer are the Particle Caster, a S6 AP-0 1d two-shot pistol (which can be fired in close combat, thanks 9th Edition) for an extra 5pt and the Transdimensional Beamer firing at AP-3 3d but a measly S4, for 10pt. The value of these is debatable but Wraiths do get the Slinking Strike rule to allow them to fall back and shoot.
The most direct comparison that can be made is with new Ophydian Destroyers, considering they have the same base price, occupy the same slot and borrowed their original design. And they do come with much increased melee damage and a very handy inbuilt Deep Strike. In general Wraiths are not the biggest damage dealers, but that's not their selling point. Thanks to their high and free movement, ability to fall back and shoot and troll save, Wraiths are more about their ability to stick on the table and effectively weave through the battlefield.