If Endowment were killed, would the Returned still come?
Somebody needs to hold the magic. If no one holds the magic, the magic will start to gain sentience. Interesting and bizarre things happen then, so I would say yes, but with the caveat that with whoever picks up the power or what happens with the power could end up changing that.
If you are viewing this on github.io, you can see that this site is open source. Please do not try to improve this page. It is auto-generated by a python script. If you have suggestions for improvements, please start a discussion on the github repo or the Discord.