Off the cuff, but what if M is a parasite deity that's taken the place of the real Necromancy god, twisting necromancy into something evil, and it's the real god who's trying to contact us with those invisible text messages?
Perhaps M is an alternative god whose worship was ushered in by Balkoth, driving the more conservative gods of Necromancy to near-death through faith starvation even before the Golgothans lost the war. I think that syvarris was on to something when he speculated M was the driving force behind the warlike nature that necromancers seem to default to; giving in to M seems like an incredibly bad idea.
I vote for more stalling in the dreamscape via mining for more info about the Necromancy pantheon.
Uh. No. Whether this Necromancer-God is real or a substitute or dead is moot point. We know three things.
1) Its Evil, or at least it doesnt appear to follow rules like our own. Additionally, we have no idea what its motives (if any) are. Its unpredictable, and that makes it dangerous. Theres no way we could safely approach it
2) Its much, much, MUCH more powerful than us. I mean, its a god. As long as we stay out of dream-land, it really cant influence us much. Other than necromancers, it doesnt have that much contact woth the real world (i hope)
3) If we are in a dream, we have zero help. Unless we find some sort of elven voodoo doctor *sneakily elbows monk12* who could help us, wed be taking on a god and whatever fiendish apparations he brought with him. Or maybe Eko could join us if he probes pur thoughts. Or maybe hed see Ms real form. I dunno, but the possibilities are quite intriguing
Then again, we could just YOLO the hell out of this, but at the very least we'd want to have Eko to shake us awake if we start chanting the instructions for artifact mug crafting or whatever
Edit: Get out now, then consider options. Theres no way this is gonna go well of we are unprepared. Say you want to think on it and tell them to come back tommorow (sleeping). Also say you arent doing anything till Omos safe. Your a necromancer. This is like a very rare oppurtunity for them. They'll probably listen to your (reasonable) demands. We are gonna have to confront them, but get out for now. Think of this Freddy-Krueger style. Falling asleep randomly=Bloody Evisceration, Trying to stay awake= Delaying of Inevitable, Going in with knives (Like the chick in the third one) and since we arent addicted to heroin, well be be relatively ok.
Edit-Edit: Always listen to voices in your head. Totally good idea. Seriously, lets go with this guy on this one. But we need a name for him. I vote for "Li'l Buddy"