Hi, I know I'm very late to this, but I just found and hatched a Barioth egg from a rare den in Darj Snowfields. I found the egg right after completing the story quest to cleanse the Pondry and Babda kinship ores (when it tells you to go to Darj to access the next area); a Barioth was the monster guarding the Egg Lair when I got inside. I'd not seen one anywhere in the game up until that point.

You can get a Glavenus egg in the subquest den from Generation gap, which is a 5* special subquest in which you fight a Rathalos in the Pondry Hills area. As far as I'm aware you are guaranteed a Glavenus egg from this den, it's unknown if you can get a rare gene egg from this nest. Happy hunting riders.

You can also get White Monoblos in the Monsonne Plains

ive found that glavenus has 2 other egg variations, pink being the main colour with either yellow or red lightning bolts

I too got a Black Diablos in Monsonne Plains. It was even before getting Ratha.

I still can’t find the Black Gravios n the Volcano. Pretty sure I can’t get it yet.

I found the black dialos during the desert missions. Like right after going to oasum. Basically i couldnt even use it yet.

MasterChef933 around when in the story did you find the black diablos there?

If I remember right black gravios was a chance from the rare dens. and even lower of a chance in the normal dens. It's all down to getting lucky with the drops.

I found black diablos in monsonne plains.

Can’t for the life of me find a Black Gravios in the volcano. Someone found one?