Totally normal — you didn’t create a mutant egg. You just overcooked it.
That green/gray ring around the yolk is a chemical reaction, not spoilage.
What’s happening
Egg whites contain sulfur.
Yolks contain iron.
When you boil eggs too long or at too high a temp, sulfur + iron react and form:
ferrous sulfide → that green/gray layer.
Is it safe?
Yep.
It looks ugly, texture gets chalky, but it’s 100% safe to eat. Just a quality issue.