Not much is known about Coldheart, largely because no one gave a fuck about her. Coldheart apparently worked in a government research facility and was fired and on her way out the door she decided to steal a few things around the office. Nothing major, some pens, a stapler, and some swords that give you ice powers. She used those swords to wage a war on super heroes and villains alike because her son died as a by standard in a super hero battle.
While attacking both Spider-man and the Hobgoblin she rambled on about how hero and villain alike operate outside the law and the heroes don't care who gets hurt and they have no accountability blah blah blah. This is a woman who stole government technology and became a costumed super being because she hated super beings. Wow. I haven't seen behavior that insanely self contradictory from a villain since the time Shredder sang a song about how much he hates music.
She fought Spidey that one time and then the only other time she was seen again was in a fight with the New Warriors in the beginning of the Marvel Civil War series. She was killed in that fight. Kind of interesting that a villain who bitched that heroes acted recklessly died in a fight where the New Warriors acted recklessly which resulted in half a town getting blown up. Part of me wonders if that was intentional on the part of Civil War writer Mark Millar, but somehow I think Millar just went through a Marvel Encyclopedia looking for some obscure villains he could use as canon fodder.
So why do I even remember her? Well, when I was first getting into comics in the 90's I used to like to buy Marvel and DC trading cards. They were a lot of fun and actually helped to get me up to speed on some of the characters. I remember getting the above card in a pack and thinking she looked pretty, if you'll pardon the pun, cool. The ice swords look bad ass. But once I finally got to read the back issue I was unimpressed.
She had an interesting look and MO, but I hope she stays dead. I wouldn't mind seeing someone else find the tech and take up the mantle. If that happens let's hope it's someone with a better thought out motivation.
Rest in peace Coldheart. You died so Mark Millar could add to a body count, we hardly knew you, and we barely cared.