At this point literally any mysterious character is Alpharis

Having done a little research of my own, I believe that Alric is a time traveler. The Jericho Reach contains the Hadex Anomaly which affects the passage of time, even trapping derelict ships in stasis. I believe that Alric knows when his brothers are in danger because he has already lived through this period of time. This would explain his extensive knowledge of the Necron Dynasty of Suhbekhar, which has only awakened very recently. The temporal effects from the Hadex Anomaly would also potentially explain the existence of the Watch-Fortress Erioch, which was found upon the arrival of Imperial agents within the Jericho Reach to already be millennia old, yet it clearly fits the design of the Ramilles Class Star-fort. In short the fortress predates humanity in the Jericho Reach.

Further research has uncovered an even more terrifying possibility, that Alric could be a Necron consciousness within the body of Space Marine. Ozkan the Codifier is the lead Cryptek of the Suhbekhar Dynasty who has been secretly using his mastery of Transmogrification to attempt to restore the Necron race to flesh and blood. He has experimented upon many different races, producing many failures of insane monsters said to be far worse even than the Flayed Ones. None have proven to be strong enough to survive the process. He has recently come to the idea that the organic perfection of the Space Marines may be able to survive the transference process.

He's really a bunch of squirrels who learned to pilot terminator armor.

Calling it now: Alric is really an Alpha Legion plant, placed in the Deathwatch to make them think the Necrons actually exist instead of just being Alpha Legion spies disguised as skeletons.

The idea of a custodies going incognito within the deathwatch sounds like a really interesting theory to me

This guy seems awesome. Anyone that rocks up on a ship in their own unmarked terminator armour is a badass in my books

Deathwatch Grey Knight

When you gotta stomp some chaos xenos

He’s one of the Fallen that DIDN’T go renegade and chose to repent that wasn’t going to the nearest Dark Angels recruiting office and signing up

We all know the real answer is that he's a giant Watcher in the Dark

Inquisition: Knight-Warden.  How is it you always seem to be in the right place at the perfect time?
Alric: Uhhhhhh... The Emperor protects?
Inquisition: Oh.  Carry on then.

Dark prophetic visions? Definitely a Night Lord!

Sweet a new Marine mystery video

It's Omegon getting back in the game

A nice midnight snack, thanks Remleiz!

1. Time-traveling space marine.
2. Some guy who heard the Emperor and went all-out, stealing terminator armor, a ship and going to the Deathwatch for ... reasons.
3. A Necron experiment or someone released from a certain Necron's museum.
(Amazingly unsaid) 4. A loyalist from a traitorous bunch of Space Marines that got freaked out by something revealed to him, and had enough pull and evidence to stay an inquisitor's hand.
5. Alpharius/Omegon/Rumored Triplet Brother of Alpha Legion (will we get a video on the third bro?)
6. Some Astartes ripping off Cypher's style for ... reasons.

I imagine he's time displaced and his "visions" are just events he remembered and intervenes in. It would explain his knowledge as being the sum of his experiences in the DW as well.

My theory is he is from the future. He intentionally or accidentally found himself cast thousands of years into the past. Commandeered a ship calculated a course that would have him arrive on a certain day. Scoured the paint off the armor. An is now living out the historical events he read about or already lived through. He is not changing the past he is the reason events happen the way they are supposed too. His past self might even be one of the Space Marines he has already saved.

Mindshackle scarabs. Calling it now.

He knows too much about Necrons to not possibly be a servant of theirs.

How did I never know of this awesome character!?

Alternate explanation, the Night Warden is loyalist Night Lord.