Heroes of the Storm already features a whole bunch of Overwatch heroes, so the upcoming arrival of Mei shouldn't come as too much of a surprise. However, in a bit of an interesting twist, Mei will not be joining Heroes of the Storm as a DPS hero, but rather as a tank!
Instead of focusing on freezing enemies and then shooting an icicle through their face while smiling like an absolute maniac, the HOTS Mei will be all about controlling and displacing her opposition. So while she won't be as deadly as she is in Overwatch, her mere presence will still spell doom for everyone that finds themselves isolated from their team.
When it comes to the actual abilities, you can find out what Mei has to offer through the recently posted preview trailer. Have a gander, she seems like a fun hero:
You can check out all of the details behind Mei's abilities, as well as the balance update she'll launch alongside with, over at the Heroes of the Storm website.