Today I went to the temple in Gnisis and was going to steal the ash mask but i couldn't take it, so i went to the console and tried to add it to my inventory but at the end of the ID it said _fake. Is it true that the ash mask in Gnisis is a fake?

Yes- the one on the display is a replica of the original, presumably created for security.

The real one is in the one in the shrine on the pedestal behind the fake mask. Activate the golden panel and donate a Cure Common Disease potion to open the shrine, see the mask, and recieve the blessing.

Neither of them can be removed from their respective places, nor can they be equipped.

Thanks for the info. I was just curious.

Of course, you could always create a modded mask with equal stats as those found on the Vivec mask. On the other hand, you could also mod new stats, reflective of Vivec's nature. For instance, +5 to Being A Dirty Liar, +3 to Hiding Behind Bad Poetry and +7 to Backstabbing Your Friends.

oh dont be so mean about vivec. He only did what most people would do with almost infinite power.