Mystery Creatures/Ships (*SPOILER*)

[moeity]

WTF are these things? I saw them in the citadel right before you go up to Breen.

 

[MiccyNarc]

Crab and Mortar Synths, baddies that you'd better be glad you don't come in contact with outside the Citadel.
It's quite obvious from their coloration that they were once Antlions, but the Combine modified them.

 

[burner69]

I rekons sumthing we'll see in an addon sumtym soon.

 

[Nostradamus]

from guide:

Crab-Synth and Mortar-Synth

You have only the briefest glimpses of these strange, inhuman contraptions: self-replicating and part replacing synths, the backbone of the Combine's subsequent armies. Crab Synths with their sharp mandibles and close quarter ripping fiends, while Mortar Synths untilize biochemical armaments and shells to wreak havoc on the humans they are about to destroy.