massive w.i.p for me and my bf. idea came to us after we were talking about a world extinction and rebirth could be from, leading to us brainstorming ideas till 1 am 

idea so far-
1. something in the world had caused natural animals to start dying out (eventual all did) leaving scientists trying to find a way to make them survive. the result ended with once extinct or mythical creatures to come back and survive.
2. in time more were made- some being used for experiments, some released into the wild and others were kept as pets or work creatures.
3. special and rare variants of these creatures can be found but you would have to be lucky to find them (so far this is only spectre, radioactive and elemental) while robotic can also be obtained as a common but special variant 

(more information to be added as we think)