The first batch were some kind of fairy looking things. They became the guardians of various successive races.
The second were the Dwarves. This version were slightly different. Strong, Durable and highly intellegent. They were "Immortal" (Read: Indefinite Lifespan). However, they couldn't use magic (Psionic Waveform) and were incapable of reproducing. As such, they gradually died out as the occasional death occurred.
The third were the Elves. Like the Dwarves they were immortal, but they could also reproduce. Because they were capable of using magic, they looked like an excellent creation... Until it became apparent they only had a limited ability to reproduce, and would eventually cease to do so. The two collectives decided to allow the Elves to worship them, to increase attachment or whatever.
The fourth were the Trolls. They were internally flawed, making them the first mortal race. They didn't get along with the Elves at all, who felt they were mistakes. Lots of deaths there. Trolls apparently can use magic though...
After this, the two were to weak to continue. They sealed themselves off somewhere, in the faint hope that they could wait it out.. or something.
“She'd become a governess. It was one of the few jobs a known lady could do. And she'd taken to it well. She'd sworn that if she did indeed ever find herself dancing on rooftops with chimney sweeps she'd beat herself to death with her own umbrella.”
― Hogfather