Holla, just poking my head in here to say YES THIS IS ALL TIERIA-APPROVED. Tieria summons his NP, defends everyone, Sephiroth and Elena make their escape. Party disbands.

Tieria wants to go after Sephiroth with the NP because he's clearly a nasty piece of work and an intentional conflict-instigator, and will attempt to do so. However, Roxy will use a command seal to prevent him from pursuing as Tieria doesn't have a snowball-in-hell's chance of winning. Essentially, this part will have no bearing on anyone except Tieria and Roxy.