I have a question about these shape-shifitng aliens from Mark of Xenos - since it's more of a 'fluff' question that a 'crunch' question, and since it might contain spoilers that you don't want your players to hear, I thought I should post it here:

Do they have some ability to read minds that allows them to speak normally as the person they are mimicking? I can't find anything about that in the description, and their stats say they speak no language at all (-and not because this is Black Crusade or Only War , which dump all but the most bare-bones skill lists from their descriptions, usually leaving out what languages are understood)- is that intentional, or an oversight? I assume lachrymoles existed in 40K lore prior to MoX - does anyone know if they can actually converse, or do they just mimic sounds without knowing what they are saying? I tried looking them up on Lexicanum , but didn't get any results from the Search function. It seems like they are supposed to be the 40K equivelant of dopplegangers, but if they can't converse, their infiltration ability is severly curtailed…

Reading through the "Charnel Spectre Incident" leads me to believe the Lacrymole are capable of communications among themselves (at least) but that's not to say they can't have picked up Low Gothic. Even so, depending on the environment and their experiences with it it's entirely possible they may have learned a common language, or can have picked up enough to pass themselves off without close scrutiny. Something you could do it have one simulate having taken a severe wound to the neck, which would imply to PCs that it is temporarily mute. Remember that there is a sidebar in the beginning of Mo/tX that specifically suggests GMs alter the creatures to fit their needs.

Using similacra/dopplegangers has always been a challenge for GMs. The best (and oldest) trick is having the double imitate a PC, walk out of hiding and start attacking its lookalike, calling for his Team mates to "Kill it! It's an impostor!"