The pulse was simple to follow once one knew it was there. With trained ease Zuriel travelled towards it.
Sure, the deck plans were not the same as on a cruiser, but the design philosophy was similar enough that he could easily navigate, even within the ventilation systems.

At one place he had to materialize, to open a sealant duct which formed a vacuum seal. It took a mere few seconds.
Being so much closer and with no interfering walls, Zuriel could now easily see that it was indeed the pet psyker of the unarmoured marine.
He was positively glowing, being this close to him was even invigorating.
Behind the two a billowing cloud was spewing down upon the floor, in complete silence. It moved towards airflows, defied gravity and once it had formed behind the pair it began to close with the psyker.

A mere couple of feet behind him, a pillar of rotating black smoke shot up, formed the dread magi whom stepped forth and took his left arm around the shoulders of the heretic psyker.

-"You should be careful with your gift, you never know what monsters lurk in the shadows." Zuriel said loudly to the panicking psyker, who gasped for air after the complete surprise.
The marine of course did not, being of sturdier stuff than a mere human.