The confirmation of the Forge World jigsaw as Deathshroud this week leads me to the first review of Forge World's Horus Heresy Book 1: Betrayal. I'll be using the tag "HHReview" throughout this series and will eventually cover all the possibilities in the same way Warpstone Flux did for the new CSM codex this year.
The Deathshroud are the chosen of Mortarion's Death Guard. In essence, they're terminators with 2 wounds, always scoring (despite being elites) and come armed with deathshroud power scythes (also known as manreapers) and hand flamers with chem-munitions (i.e. a flamer with shred and gets hot!). The scythes are interesting: the deathshroud may replace their natural number of attacks for a number equal to the number of enemy models in base contact with them and perform a sweep attack. Lots of S5 AP2 attacks are deadly to most units in 40k and can certainly bust light transport tanks.
I see them in two roles: (a) as shock troops, and an escort for a terminator praetor, even Mortarion himself; (b) a deep-striking nuisance unit that can disrupt back lines and claim objectives with near impunity.
Here's a couple of example builds:
4 Deathshroud terminators, melta bombs, Land Raider Phobos dedicated transport with frag assault launchers (450 points)
This is a real points sink, but could be very worthwhile. Attach the Death Guard praetor or Mortarion himself and go forth and assault the heart of the enemy, especially large hordes of elites and opposing terminators.
3 Deathshroud terminators, melta bombs (145 points)
A reasonable price for a small unit of genuine nuisance that demands to be dealt with by any opponent. Not invincible, but opponents will think twice before charging them. Run a couple of these squads via deep strike and disrupt the enemy. Charge any objective holders as Mortarion commands. Take, control and hold said objectives in the late game.