...so I arranged a marriage between my daughter and the Khagan's heir. Then all I had to do was murder my son-in-law, wait for the elderly Khagan to die, and boom. The Mongol emperor is now my 6-year-old grandchild and ward. I think I'm safe from Mongol aggression for the time being.
By the way, it was the fastest and easiest murder I ever committed. I don't even have any Intrigue perks. 23 agents joined immediately. I guess those conquered vassals really hated their overlords.
(Now I just hope my leper grandson survives childhood.)
IKR? I never expected Finnish paganism to spread so far beyond my borders. It's not just the Mongolian Empire. I think it's actually the dominant religion in the world right now by number of counties.
After researching the scripted behavior of the Mongol Empire collapsing and the bugs it can cause for player characters, I've decided to play it safe and NOT let the future Khagan of my dynasty inherit my primary title.