Basically a nuzlocke in every way, except for every new Pokemon you catch, or every area you can get a Pokemon, depending on how you set your own rules, you immediately trade said Pokemon for an egg, and that will be what your team is. You normally get others to trade you eggs, so that you don't know for sure what you'll be hatching. That's the fun of it.
Muk woulda been useful too. had one in a nuzlocke m'self