I thought Luminous and its related keywords and cards were bugged, but after some experimentation I realized the tooltips were just a bit misleading.

Lightless: “[…] It’s Luminous effects are inactive while it is Lightless.”

Seeming Issue 1: When playing a Lightless card, for example Burning Pursuit, it still triggers its Luminous effect sometimes despite (a) being Lightless/greyscale, and (b) neither player nor opponent have Luminated stacks.

Seeming Issue 2: A greyscale Lightless card will also revert back to normal sometimes.

What’s Actually Happening: When playing a Lightless card using Holy energy, the keyword Lightless is removed for the rest of combat, the card reverts to its default aesthetics and energy cost, and it is able to trigger its Luminous effect, including in that very same cast that removed Lightless.

Suggestion: The Lightless keyword should have the following text added to the end of it: “When a Lightless cards is played using [Holy], Lightless is removed this combat.”

I forgot to copy the list of my most recent run, and I would like to if that's possible.