User blog comment:Omega natsu2/Chapter 364: Tartarus Arc, Part 1: Immorality and Sinners, Predictions./@comment-4449950-20131214020850/@comment-7418318-20131214084103

@VenomDragon: The three people are tied to the seal, not the trigger. I'm sure even if the seal is undone, Face won't explode without someone triggering it.

Think about it: How likely is it under normal circumstances that someone learns the top-secret information of Face's very existance, find its also top-secred location and arrives there while all three seal-bearers are dead, without the council noticing and casting the seal on other people?

There's also the possibility of additional protections that Michello either hasn't mentioned yet, or wasn't aware of, like a physical key, traps at the entrance of the building, guards,...

Maybe Immorality and Sinners both refer to the Demons. They certainly showed that they don't care about morals (Jackal's quote about Humans being playthings for example) and they commited plenty of sins already.

So maybe the next chapter will tell us a bit more about the past or the motives of Tartarus.