[X] Yes
-[X] Approach the Sigillite.
Malcador is in a precarious position right now and we can exploit that to our benefit. He has resources beyond strictly military that can help us keep this from getting out of hand politically, and he's pragmatic enough to not hold a grudge even if he dislikes Angron because he can almost certainly see the value in needing to take care of an insane superpowered serial killer in charge of an army.
As well, this is a good opportunity to bring up something important for Angron's overall goals. They aren't in line with the Crusade. In fact, most everything Angron is about is opposed to the tyranny and oppression inherent to everything involved with the Crusade. Angron is, ultimately, going to butt heads with the Emperor in such a way that one of them is going to die.
But to get to that point he's going to have to play the game, and he's committed himself to doing so. Right now he can probably get Malcador involved in making sure this operation succeeds, and as a consequence Angron grows closer to Corax. He's who I'm really aiming for in the long-term here, because when Angron and the Emperor eventually come to blows it will be nice to have allies. So I say Angron gets the Sigillite involved and potentially off his back for a bit while solidifying Corax as an ally who might come when all the chips are down.