Crazy Glue: Ha, you didn’t think a super intelligent mastermind like me wouldn’t have a backup plan, did you!?
 
Celestia, your an idiot.
 
She just put two masterminds in the same room(in real life, that historically has lead to bad things)
 
Speculation:  
So the BFF’s will without a doubt break out of Tartarus, and most likely will break out “Tartarus Prisoner Number One”(Grogar The Necromancer) the three will then recruit Chrysalis then Grogar will use his necromancy to bring King Sombra back(using his horn as part of the magic) and Sombra will attack Ponyville to deatroy the Elements of Harmony, with those gone, Sombra enslaves all in Ponyville(including Spike, Starlight, The CMCs, The Young Six and more) as part of his slave subjects, then begins an attack on The Crystal Empire. Oh and Cozy and Tierk get a stone sculpture made for them by the slaves.