Missing Monster Log?

[Gorm]

Hey hey, I've been trying to fill out my logbook for the sake of completion. Tracking down the couple trials I hadn't done, buying some blues, getting a red scrap, that sort of thing.

I'm down to the point where the only things I haven't gotten, are an Irradiant Pearl (Because Boy howdy, that's an RNG fiesta), and a monster log for something I've apparently never seen?
I've got just about 100 percent completion, so I'm real confused as to how this is happening.

The monster Log position sits just between the Parent and the (land) Lunar Chimera, here's an outgoing link to the screenshot. https://ibb.co/PYTqXqz

Point of this being, is this something everyone has got? Or am I missing something somehow? Like, what's the dealio?

[Gorm]

Ok, then what am I missing? Not only I have eaten god multiple times, I usually do it on monsoon and have the Moon enviroment log. So how is this a monster I've never seen?

[zverozvero]

Think its problem with it being split in phases. It remains 'locked' even though youve killed him multiple times. Only way to go is killing him more and log might drop eventually. I got it from final phase but i heared it can be dropped by phase 1 and 3 too as iteration of Mithrix tecnically die.

Can speed up process with artefact of Command stacking Clovers. Each clover stack is worth one extra kill.

[Gorm]

That's... Kinda goofy but I guess it makes sense as to why it's not showing up.

Thanks for the help