Continuing with the rap feuds line Jay is saying they could take subliminal shots at you (disguise) And I think Drake knows all about that by now
As for the “in the form of a favor” he could be referring to how his beef with Nas started seeing as Nas was supposed to appear on some of Jay-Z’s tracks for his debut album Reasonable Doubt which would have been a favor. Nas never showed up and it helped fuel the feud between the two.
The “In the form of a favor part” could also mean that usually beef between rappers bring publicity and popularity. 50 Cent used this method as well to make himself popular