"A Displacer Field creates an extremely weak forcefield bubble around its wearer," said Eunicornus, thinking. "When that bubble is penetrated by a weapon then it collapses, like a punctured balloon, and drags its user through the Aether until the collapse is finished, whereupon the user re-materializes. Then it takes a minute or so to re-inflate the bubble. Or... that's how I understand it, I am not a Techmarine, I just know its behavior for the purposes of combat." 

They cough. Their helmet is still on and they show no signs of taking it off. Some Astartes are like that; it makes their voices a little hard to follow sometimes, but some MK4 helmet types have the options for subtitles.

"That is to say, it is possible to shoot someone through a Displacer Field," said Eunicornus. "If you aim exactly right and have the correct angle a shot can make contact with the target before the bubble collapses, and then the bolt gets dragged along with the user as they're teleporting. It's impossible to shoot someone twice though, the collapse will always initiate before the second round will make contact. This means they're excellent protection against sustained, automatic fire. This also means they're excellent for heavily armoured individuals like Tech-Magi who can shake off a single bolt round, teleport to safety and use the moment of disorientation to charge their weapons and activate optic arrays to re-orient. Killing an Archmagos [i]outright [/i]with a single shot, though?" They let out an impressed breath, a crackle of static from the helmet speakers. "That's a [i]hell [/i]of a shot. That's something I don't think anyone outside the Vindicare Temple of Snipers could do reliably, especially during a breach and clear. Maybe a robot? Even then they'd have to get really lucky..."

They trail off in thought, tapping their fingers against the hilt of their sword.

"The second exchange is easier, though," said Eunicornus. "If the assassin knew where the Archmagos was teleporting to and was able to shoot them as they were materializing then either they could see the future or they had sabotaged the Displacer Field. There are lots of Xenos that can do either or both. It's why we don't use the things ourselves - not reliable enough, they're civilian escape hatches and not military standard. Necrontyr phase-tech is more advanced and doesn't have those limitations, but this is as close as we can get to train against it."