Polaris is an incredible ally, and it shouldn't take much convincing to see why. She can give you two blocks and 4 damage for 4 resources, which edges out even Mockingbird on value. Against stalwart villains, giving your hero tough is better than stunning, and you don't even need to have an X-Men hero since she can give the tough to herself. Because she has the X-Men trait, she is insane with the X-Men archetype cards like Danger Room and Utopia. She is the best combo piece with Mutant Protection, which effectively reduces her cost by one. Polaris is a protection staple because you don't have to put any extra work in for her to be good, and with a few combos she is insane. Put her in your protection decks (and Cyclops decks!) and don't think twice about it.
Attack: 2. Thwart: 1.
Response: After Polaris enters play, give an X-MEN character a tough status card.
Mutant Genesis #12.