Adeptus Astartes likely to be in the vicinity of Devos IV

The Blood Angels were the Adeptus Astartes contribution to the war against WAAAARGH Burkett 800 years ago.  There are Blood Angel artefacts in the Xyphonica Basilica of the Emperor Restored.  Mauven 158, another world in the Dynorwic cluster, saw a Blood Angel strike force deploy to hunt down a detachment of the Emperor’s Children three years ago.  The Long War does not only persist in the minds of those traitor astartes in the Eye of Terror, it is remembered by the descendants of their foes as well.  The ancient fight between the Blood Angels and the Emperor's Children continues - And Eidolon escaped Mauven 158.

PVP's Blood Angels.  4000 point here.  Karitas has some too.

Rune Priests, following their own arcane predictions, have led possibly more than one Great Hunt into the Dynorwic Cluster, ready to respond to further casting of the runes.  Wolf Scouts are not a common sight, naturally, but they are at large on many worlds, sniffing out the situation and following up on leads and sightings, building up a larger and more comprehensive picture than many other of the agencies involved.  The Rune Priests have seen that failure on Devos IV could jeopardise the whole Dynorwic cluster, the attentions of a Deamon Prince from the Horus Heresy make this a fight they will take on.  The presence of Lone Wolves on Devos IV already is no accident.

One of Karitas' Rune Priests.  Gregarious fellows, Rune Priests - they have lots of friends

The Brothers of the Lostwithial, a splinter of a Black Templar Crusade, have come directly to Devos IV in order to fulfil an oath to Inquisitor Blingnor of the OH.  They have already managed to alienate many of the senior command teams at the front line, even if their incessant rituals are indulged at High Command. The mysterious Adeptus Astartes of ‘One Force’, who have previously ‘punished’ Black Templar formations for over enthusiasm (when the Brothers get carried away dispensing the Emperor's Justice in population centres) are possibly shadowing the Brothers.  Only time will tell. 

Andy BG's mysterious One Force, 

Through various agencies (possibly radicals in the OH), the Relictors have learned the fate of the War Griffons Canis Fidelis, now the Khornate Belligera Rex.  Securing any of the Aroctech from a debased  titan could possibly advance their schemes quite some way.   If your purpose is to understand how the warp can effect the laws of nature, the fundamental laws of the universe, then something like a titan, even a small one, amounts to a substantial sample.  Even if it has to be picked up off a battlefield by a thousand men with buckets.

Siph's Relictors - just the middle bits.

The Brothers of the Lostwithial may be already in situ, but their force is likely already depleted by the actions they have already undertaken on Deovs IV.   They view the Blood Angels as heretical.  The view the Relictors as heretical.  When they meet the Sons of Russ, the chances are they won’t take to them either.   Relationships between the other Astartes factions remain a matter of conjecture.  For the time being. 

My vast collection of Black Templars.  Gonna need some more....

And if something attracts four disparate Chapters, then it is almost certain to attract others...

The punisher of errant Astartes.