The central flaw of Syn's plans is that, no matter how high she rises or how much control she gains, her web of schemes will always have a single point of failure: the Hesiesh guise. She's not unlike us in that regard; exposure means ruin. If we can survive long enough to accumulate the power necessary to shatter that facade (via EotUCS or forcing her into battle) then all her schemes come apart at the seams. Emperor Flame's legitimacy? Gone. Suddenly, he's just another zealot with a powerful bloodline. Her power looks absolute, but you think there aren't those who are questioning? Either individuals who weren't particularly devout in the first place, or the Immaculates who wonder why Hesiesh isn't taking the field in open battle, or where in the fuck the other Elemental Dragons are? Her position appears unassailable, but this is as much an illusion as fact. There's a reason that, even at the height of their power, the Bronze Faction never pulled this stunt; it's because it's insanely reckless. She's put all her cards on the table. If we expose her, we end the Immaculate faith, or at least cripple it almost beyond recovery.
Luseng will be difficult, of that there is no doubt, but as long as Sesus Ulyssian still lives, we can make a comeback. Fade Away burns that bridge, forever. It's an entirely different series of gambits and long shots, and relies on negotiations with the Infernals and Lunars, as opposed to mere combat (which is definitely Ulyssian's strongest area), and builds on past deeds.