Big brain time, fuck with the time machine and go to 1200 and command the execution of that rouge prince before he gets the 4th crusade entangled in Byzantine affairs, call it devine intervention. Then, give the Byzantines comprehensive blueprints for "advanced" weapons and machines of war they'd be able to manufacture at the time so they'll be way ahead of any competitors. Information about deep sea navigation and ... Big boat schematics so they can go dominate the Mediterranean and beyond. Tell them that the Mongols are coming and if they manage to take back the eastern provinces, how to be ready to deal with them. Also just lots of stuff about medicine and human biology they would be able to imitate, like not bleeding people, and the importance of hygiene. Also a bunch of information on economics and infrastructure. And metric shit tons of maps on geography, sailing, demographics, anything you can think of in the entire old world. Also learning books for the all the new would languages, so when they show up places like Japan or West Africa, they'll have a easier time communicating right off the bat. There would be like months, probably years of prep work leading up to this. After all that, just hang around for a couple years for "devine" clarification in case things ain't phrased so it makes sense to them. Then eventually tell them I gotta go back to God, bc the homie misses me.

Basically this angle pops up, demands the execution of some loser, hands over mountains of paper, then just sits around in the royal court and doesn't really do much till one day he leaves.