Wasn’t feeling too great the past few days, so decided to do a redrawing of my oldest nextgen scenario. Text from the original image:
 
“Despite looking the part of Nightmare, Black Lotus is generally actually a very gentle pony. With a body twisted by a combination of remnants of dark magic and parallel world warping, Black Lotus may rarely succumb to the loneliness and sadness she is caused by others being fearful or hostile towards her and enter a ‘Nightmare Mode’. In this form, her already flowing mane reacts more like a dark flame, the sinister tendrils drifting from her eyes become darker and thicker, and her eyes themselves become an icy white-blue with a darkened setting.
 
As her sister, and a balance of day to night, it’s Morning Glory’s job to soothe her half-sister and calm the overwhelming feelings of despair and Black Lotus’ fearsome magic. Fortunately, same as her sister, strong magic is in her blood and she is usually a match for Black Lotus, though it’s likely to leave the both of them sore and exhausted for some time afterwards.”
 
I’ve since changed a bit about Black Lotus regarding her ‘Nightmare Mode’. This change mainly applies to my headcanon that Celestia and Luna have Kirin blood, which shows particularly in the transformation for Nightmare Moon and (theoretically) Daybreaker. While Black Lotus’ change is still triggered by the same emotions, it’s due to the remnant Kirin blood having a particularly strong influence.