Sacrifice

[Ydex]

Sacrifice rewards are based on "essence" i.e. how many characters you sacrifice, and how leveled up they are. Click on "rewards" to show you. I think the levels are 100, 500, 2000, 6000, 9000, 20000, and 50000. In general sacrifice as many of the highest level hearts you have + highest level duplicate characters to get a high "essence" sacrifice and better rewards.

If you have XP shards, you can level up the hearts and characters for more essence and better sacrifices. It's really only worth it to level them up to half to 3/4 max, after that you get diminishing returns. OR you can level up your duplicate characters by using them in daily grinding. ESPECIALLY duplicate Eddies, which can be leveled up in the 2nd and 3rd Eddie slot.