So, in the actual Nexus (the base between worlds, the hub between portals 'arcs' that go world hopping), one of the players rolled 2 critical failures on the dice while essentially hunting and bartering for goods. So, rather then just LAWLCOMBAT, I decided to pull an oldie but goodie.
Hand the player something massively powerful, and wait.
So, anyone who knows gurps Ultra tech, has heard of monowire. A few campaigns prior, we had a social character who her only weapons were thimble grenades in monowire spools. Eventually she made them legitimate grenades with a robofac. Moving on.
The player found a case of these monowire grenades. Practically selling his soul when he found out what they did, he bought them up, even when I flat out told him the kill radius was farther then he could throw.
Many portals later, they land in a D&D esque world where they'd be picking up a demon-pixie new player to the game. They land in the belltower of a nice church, who is just bewildered how the group got there, as they don't seem the stealthiest or cleverest of the bunch.
Soon they realize, omg cult. And not just a cult, this cult knew about the portal, they worshipped it, and even had a magical artifact to make more portals. Could be the cause of the entire campaign... LETS START A FIGHT (they weren't, just simple cultists with daggers and a magic book).
As the battle moves outside, the church is encased by a stone wall, scalable but will take time. The large church following pours out, grabbing whatever weapons and torches they could to go after the party. Many of the party are wearing high tech battlesuits, so really they're not in that much danger (We had a Saiyan, a Mass Effect soldier, A werewolf in battlearmor she got from another pc, and a TL0 mayan scout. The only one without armor, who was fleeing at the moment).