This card needs to be errata'd. On the printed version, it displays a (Star) Boost icon without any accompanying text to explain its effect. .
Combo Enabler
Looks pedestrian on the surface but it enables some cross tribal allies to become playable.
Where this card really shines is as an enabler for Mutant Mayhem. The combo can be a very strong with Monet St. Croix and any X-Force or X-Men character like Beast or Deathlok or Hope Summers or Pete Wisdom or Professor X
Sometimes it's better to not use ally (in the next turn prepare for blocking) or even hero. From solo perspective if you can remove scheme by one card, this is very good. What's more 6 threat on one scheme is very rarely (but for example Under Pressure in campaign got 6 threat). In term of effiency this is 1 card per 2 thwart (+ exhaust). In justice this is not as much exciting, but in multi-aspect build this can really help.
New expanions on horizon (Agents of Shield) probably will raise potential of this card even more.
Solo this card is (A-C) B+ In multiplayer B-
M is one of my favorite allies from the Magneto hero pack. Abilities aside, she provides acceptable value from thwarting 3 times then blocking. Her Enters Play ability is similar to Valkyrie, killing a 3 health or less minion in play (even bypassing Tough statuses). Although it won't always have a target, I love having this ability within my toolbox of allies for cards like Make the Call, Cerebro, or Call for Backup that always help us find the perfect ally for the moment. If we can upgrade her hp with Uncanny X-Men or Team Training (cards that are totally fine to play on their own), she can take out even bigger minions!
The 3 ATK stat also presents some interesting possibilities. It's probably worse on average than 2 ATK with only 1 consequential damage, but effects like Teamwork or Mass Attack that ignore the consequential damage will benefit from her. She can also use it on her last hp where the second consequential damage isn't as awkward, or it can be a tempo boost when needed if you need to prioritize that over efficiency.
Lastly, M has two great traits: Psionic and X-Men. She's a fantastic hit for "To Me, My X-Men!", turns Cerebro into a full-deck search, can be played by Psionic decks using The Power of the Mind and Psimitar, and has the many benefits of being an X-Men. Maybe not quite a staple-level card due to the abundance of great allies and need to have a minion in play, but extremely strong, especially in Trait-focused decks.