Monster Hunter

No, that's pretty much it. My only advice is to keep persevering.

Yeah, just brutally and mercilessly repeat the Rathian and Rathalos quests, especially Capture the Rathalos for the better Los rewards. It is extremely rare, I've gotten 1 from abtou 20 Rahalos and Rathian. Good luck!

You can trade Monoblos spines and crimson horns for wyvern marrow with the elder in the forest & hills.
I think he's in area 7

Beat Los and Ian much,,(It's better if always stay alive until you beat them)
for Los, cut off his tail brings better rewards in the end...( I think in his capture quest)
for Ian,, it's rare.
I've ever got it from her tail. You carve it vertically with her off-tail.

Keep on killing rathalos or trade for a monoblos spine in the fores and hills place.
hope this helps

I've found out that you can get it easily if beat los and ian in TP.
I always get one from los after I beat him...
4 d' better carved try to carve from his wing...
oh yeah... but b'4 it,,, hoping u can beat them and clear the mission (Oh my God)..

I have the same prob man. I found that you can raise your chances of getting the marrow if you cut and carve rathalos' tail. When you carve rathalos, you have a 2% chance, but if you carve both the rathalos and his tail, you now have double the chance.