The first shadow oath is the oldest but most inhumane oath since the beginning of the Shadow Unit. After all, the very first shadows used to be people who committed crimes against the throne.
For both Elov and Valtis.
It was terribly one-sided where the shadow had little to no freedom. They could horribly be punished too since they had no choice but to listen to their master. The master doesn't even have to care for the shadow and they are usually used as meat shields.
Of course, there were many different verses of the oath. Each punishment always takes something from the shadow and they usually get 'tamed' when their master pours energy into their bonds. It's especially bad when the shadow's master will get terribly pissed off for one reason or the other.
Yet there are versions of the oath that are temporary but the shadow loses something anyway. They also won't get unfairly punished by their master or properly won't get punished at all.