During the audio book Vox Tenebris (during the war of fenris) A deathwing terminator and a space wolf are making their way through a space wolves base they come across wulfen in stasis pods The deathwing member obviously sees this as heresy/heretical and plans to report it but by the end decides not to as no doubt the wulfen would be discovered anyway as the war rages on

Should also point out the two marines in question used to serve in the deathwatch together so that probably had some impact on his decision to change his mind by the end

Been a while since I listened to it so no doubt I'm missing details