Ruby chest no Demon chest?

[Silrain99]

Does opening a Ruby chest in game not give a Demon chest every time a you successfully complete a mission?

Just completed an unearthly run to find the Ruby chest I collected in game did not show as a Demon chest in end screen or in my trinkets.

[Libbitina ♥]

Gives +100 rubies :)
Doesn't give you a demon chest no

[Bongwater Pizza]

What made you think they give you a demon chest?

[Sonnenblume]

Ruby chests and demon chests are separate entities entirely. Ruby chests give 100 rubies. Demon chests add demon chests to your inventory.

Keep in mind that completing card pieces has a 20% chance of giving you a demon chest on higher difficulties. You may have been confusing this additional demon chest as coming from opening a ruby chest.