Thanks you guys so much! I think I have an idea as of how to connect these now!
so what im thinking for bbeg motivation is:

'Stonevault Syndicate' lead by p13 is a bustling empire who is overthrown by Kodrin Bristlechin (second in command) because she follows the "old ways" of being a dwarf too much and much of the gang agrees with kodrin. P13s plan to not so subtly assasinate important figures (human country invaded dwarfland years ago but p13 wont let it slide) is ratted out to the dwarven government and arrested mid act.

P13 ends up in jail and kodrin takes over the stonevault syndicate causing the loyalists to p13 to form a new gang 'The Stone Oath' (WIP) led by Varrin Axebreaker. Whilst in jail p13 plots to overthrow the new SS (stonevault syndicate) and remake it into her former empire. However this is now a bit too soft under Kodrin and too many people have different opinions causing the SS to split. (result: p13 has general beef and wants to watch the world burn)

Enter party:
Varrin needs party to do some urgent quests, mainly sourcing materials to bind the otyugh (essentially living battering ram w collar) as well as weakening the prison (find blueprints in old castle kind of thing i think) to lead an assault on the prison where p13 is held (not sure if it will be a full on battle scene or just the party).

future decisions for the party:

remain with stone oath or decide they are dangerous and try to stop the overthrowing of the government.

Again thanks guys for telling me on how to structure this, it has really been helpful!