Hello!

Thank you for the report. When a champion is sacrificed all of his equipment is deleted as well.
There is no warning in the game when a player is about to delete some equipment but it will be added in the future. 

Meanwhile, I recommend that you lock champions with equipment so that you won't be able to sacrifice them.

Well congrats I'm done with this game apparently I've been sacrificing all my gear for the last week because as a new player I didn't know this and there's no warning. Now I've lost all my epic sets I got from starting your game with no way to get them back and this bug has been in the game for at least a year now without being addressed. This is massively upsetting and disappointing.

I'm assuming at this point it's not actually a bug or an oversight but another way to make people grind. It would be one thing to put it in the new player tutorial and warn people but to completely omit it is beyond stupid. Why bother giving new players anything at all to get them started if you know they will lose it anyway because they don't know to remove it.