The Beginning
Years ago a friend of mine showed me a map of The Inner Sphere from the FASA Mechwarrior universe. I had been toying with the Amber Diceless RPG System at the time and had run a few adventures, but didn't care for it. After seeing the map I got the idea of it as a map of Creation, and the colors as the borders of different realms ruled by the player character's elders. And thus, Nexus was born.
Nexus
Nexus is the city at the center of the multiverse. It sits atop the Locus which is the pattern scribed onto chaos by Magnus which has shored up Creation against the ebb and flow of the chaos beyond as long as most can remember. The players are the children of the children of Magnus, who all rule different facets of Creation/Reality. The campaign tells the epic tales of their battles against both outside forces and internal forces that are trying to disrupt Creation and the Nexite's rule over it.
HERO System
It started in HERO System and was adequate, though looking back, pitiful. This was the Nexus campaign in its prime however. All the major characters, families and story-arcs came out of this time. People moved, the campaign got bogged down, and the HERO System lost its luster, requiring far too much prep-time.
MasterBook
Years later, after reading TORG, I decided to try Nexus in Masterbook. Everyone made their characters who was still around, and we played once or twice, but it never got off the ground.
Exalted
Years later, I melded much of the Exalted backstory with Nexus and even tried to use the game system. That system is crazy complicated.
Exalted 2nd Edition
Years later I took another look at Exalted, now in its second edition. It was better, and we made characters; many new players joined. The campaign ran for quite some time and great fun was had, despite the system, which is ridiculously complex and unwieldy for little gain. To be fair, I was mixing Trinity, Aberrant, World of Darkness, and Scion into the mix.
Mutants & Masterminds 3rd
Wow, this is a great system, but suffers from a crazy fast power progression. I spent a lot of time trying to get this to work, but ultimately the upfront prep time crushed it.
Savage Worlds
We tried a conversion to SW but it fell short. The super powers support is weak at best in a very lethal game. Fail. Lost players.
Masterfinder (Pathfinder)
Tired of Savage Worlds, I had an epiphany one evening about how to make Pathfinder work across all levels of play at the same time. It incorporates a lot of Mutants & Masterminds ideas but uses a slower power progression. It also uses base, raw, Pathfinder/D&D which, if nothing else, has vast amounts of pre-generated material available. Nexites are crazy powerful so far, but it is fun!
Mutants & Masterminds 3rd
I lost several players who hated my mashup system and to woo them back I simplified by switching to M&M3e, which was a major inspiration for the system anyways. One of my initial complaints of M&M3e was the prep time, but having the characters already drawn up in Masterfinder is making the conversion very easy as powers, skills, and advantages for M&M3e are limited by what they had in Masterfinder. Several sessions played and it already seems lighter and faster while still retaining much of the flavor.
And back to Masterfinder
M&M worked very well, especially with the preconceived builds from Masterfinder to guide the builds, however, the two actual players who had stuck through me thick & thin, preferred Masterfinder, so we returned to it. My problem with it, and M&M, is the crazy swingy d20 used for resolution.