Reiver

We have Sly Marbo Marines now! Piss yourself Chaos scum!

"All Space Marines are experts of the rapid strike, but Reivers take these skills to the next level. They are specially trained and equipped to launch brutally effective and unexpected assaults. They do this with a sudden fury and shocking violence, for the Reivers fulfil the role of terror troops that sow fear and confusion amongst their foes."

– Games Workshop

"Boo"

– A Reiver

Our Super Super Marines have Catachan Jungle Fighters in power armor now. A Reiver (named after 16th Century English-Scottish border raider clans), who is usually part of a Reiver Squad, is a new type of combat specialist unique to formations of Primaris Space Marines who is tasked for rapid infiltration and lightning assaults. Where the Intercessors are the defensive battle line heavy infantry of the Primaris Astartes, the Reivers are elite assault specialists given special training and wargear. The Raven Guard and White Scars are known to favor their use to supplement their own fast attack doctrines.

The Reiver squad is armed with over-sized combat knives glimmering with disruption fields, heavy bolt pistols that are more effective against armor, and "shock grenades" that prevent opponents from firing on them in overwatch and penalizing their hit rolls. Their helms are death’s heads, with their left pauldrons enlarged to provide better protection in melee.

Their armor is stripped down to be eerily silent, adapted for stealth work (and they watch veeery carefully for twigs). Reivers are a specialized infiltration and close-combat unit. Essentially, they are Primaris Reasonable Marines. They are also totally not Night Lords, even though they wear skull helmets, are used to "terrorize" enemy units, and have a bad habit of leaving enemies flayed and out in the open—this is represented by reducing opponents' Ld by 1 simply by being 3" away, stacking up to Ld-3 if multiple units are in range.

And another interesting tidbit. The skull helmets apparently incorporate weaponized loudspeakers (Possibly 'graciously gifted' by the Howling Banshees during Cawl's time with the Ynnari). Reivers "disrupt the hearing of the enemy with vox-amplified war cries and audio-sonic weaponry", which assumes both that combat is happening in atmosphere and that the enemy is capable of hearing/didn't bring ear protection, but what can you do.

Equipment

Reivers are all equipped with Heavy Bolt Pistols, handheld and deadly versions of the bolt rifle, with many also wielding a long-bladed combat knife. Reivers can also stun enemy infantry with the shock Grenade stratagem or deploy deep behind hostile lines via grapnel launchers and grav-chutes.

On a side note the “Heavy Bolt Pistol” is in a weird state of canonicity. The lead designer for the Primaris range claims it was only added for balances sake, and codexes/BL seem to be inconsistent on wether it exists or not. (See; Vox Cast 1, the fact the absolver exists and the fact they use a normal bolt pistol model).

For additional range, they can also swap their heavy bolt pistols and combat knife with the trusty Bolt Carbine which sits comfortably between the bolt rifle and the bolt pistol and comes with the snazzy little foregrip kitbashers have been adding to bolters for years

The Space Yiffs have their own special variant of Reivers known as the Hounds of Morkai, who are anti-psyker hunting teams protected against the Warp by runic wards and come with a slew of abilities that help in fucking their shit up. They come equipped with special issue bolt pistols which are better heavy bolt pistols with -2AP and carry Runic Totems that prevent them from being targeted by enemy psychic powers as long as they are not the closest target to whoever manifesting that power, as well as granting a 4+ save to any wounds inflicted on them during the Psychic phase (though it actually counts as an ability rather than a wargear). However, GW doesn't seem to have any new models for them, and the image preview accompanying their rules looks like a kitbash between a standard Reiver squad and the Space Wolves Primaris upgrade kit.

On The Tabletop

Reivers are often compared to Assault (Veteran) Intercessors and while they have the same base Primaris profile the main difference is that Reivers have more DS on their pistols (but at 6" less range) and Assault Intercessors have more DS on their Chainswords.

Reivers do get some nice tricks up their sleeves though. They have the morale diminishing aura that can help causing some damage in the morale Phase and they have excellent mobility. They can now take both the grav chutes that let them deep strike and the grapnel launchers that let them move over any vertical terrain without issues.

They have the Shock Grenade keyword which lets you trigger the equal Strategem for 1 CP that prevents Overwatch AND gives the opponent -1 to hit in combat, which is pretty nice.

Overall they do exactly what they are designed for, being a mobile disruption unit which looks cool and has some nice tricks to play with.