Notes:

Okay, so here's the thing. In the hard modes of F.E. 11, Medeus the Shadow Dragon has a speed stat of a perfect 30. Marth caps out at 25, which means Marth has absolutely no chance of surviving a single skirmish with this beast due to the fact that he'll most certainly double-hit you.

HOWEVER.

if you constantly trade the starsphere and lightsphere between the two ballasticians (Jake and Beck), you can slowly but surely whittle down his HP with little-to-no risk. Just make sure they survive, okay?

Also, this can only really be done in the last 6 or so chapters, so it's not as broken as you'd think. It does kind of suck that you have to sacrifice the Falchion as collateral for it . It does also kinda suck that the Falchion is next to useless in this game's harder difficulties, but this is a really funny strategy nonetheless.