Wait, I thought Dani just made... bows and arrows (ugh) like Psylocke does with daggers. What's her energy weapon deal?
In the 90s, a lot of Claremont or Simonson created characters with interesting or limited powers that required thoughtful plotting were converted into doing generic energy blasts that were easy to draw in a static splash page, with varying degrees of plot justification. New Mutants and X-Factor teens were big victims of this.
Richtor: earthquakes --> green energy blasts
Boom Boom: time bombs --> yellow or pink energy blasts
Dani Moonstar: illusions --> bow and arrow shaped energy blasts
Sunspot: can become super strong, but not invulnerable for limited periods of time --> black energy blasts
And weirdly, in one of the worst examples of this trope, it even happened with characters whose power was energy blasts!
Havok: energy blasts too dangerous to use without risking murdering someone, a major source of angst and why he hated being forced into superhero nonsense and was scared of his powers --> generic yellow energy blasts, can be so weak they don't break a practical joke can of mayonnaise
Some of these characters recovered (Boom Boom and Richtor basically have their original powers again now), but Dani was kind of a long-term casualty of this trend. It's really too bad, because she was a great character in Claremont/Simonson's New Mutants. She basically becomes the main character of the series for a while.
“Karma” really feels like the more appropriate name for someone with Nightmare Vision powers.
Karma's first appearance was in a Claremont/Frank Miller issue of Marvel Team-Up (#100) that is probably worth reading if you're going through the original New Mutants. Like their Wolverine series it's a fairly strong issue but also it's kind of a mish-mash of vaguely Asian tropes at points and her name is part of that.
You know, I’ve read all of the current run of New Mutants; a relaunch that exists to let you become familiar with the characters, and have started reading the original Claremont run, written by a guy who had a pathological need to explain everyone’s deal at any given opportunity.
I still couldn’t tell you what Danni and Karmas powers are, if you put a gun to my head
How far are you into that run? If you're not to issue #3 yet, keep going. What her powers are is really central to the first arc.