Marissa is a friendly girl that is shown to be at odds with Trickster's way of thinking, despite following his orders. She would prefer not to be involved with the Travelers and Coil, but it was her only hope of saving Noelle and returning to Earth Aleph.
Marissa's power allows her to create a miniature sun, hundreds or thousands of degrees in temperature, that she can manipulate at will, even while the orb is out of sight. It is bright enough to leave spots in the vision of anyone who looks at it it.
She is able to create orbs the size of a three-story building, but even small orbs are dangerous. One the size of a beach ball was capable of forcing a fifteen-foot-tall Lung to collapse from the heat.
Can put out fire by flash burning oxygen and absorbing heat and flame into her sun.
Temperature completely normalizes close to her, preventing her from getting burned. This effect extends to her clothes and the ground beneath her for about five feet. It doesn't extinguish flames, but prevents them from damaging anything.
It took time to form the sun, with repeated flickers of flame appearing between her hands. When sufficiently transformed, Lung's pyrokinesis was able to prevent her attempts to form the orb.
When the Simurgh attacked Madison, WI on Earth Bet, she took several buildings from Earth Aleph - including the building Marissa was in - which left her stranded on Earth Bet with her friends. After Francis found a suitcase full of Cauldron superhero serum, they each took one except for Noelle and Oliver who only took half a dose.
↑“Then tell me where to move it,” Sundancer’s eyes were closed. “I can’t see that far.”
“Out further, left, left, left,” the miniature sun slid twenty or so
feet with every order I gave as I tracked the enemy’s position and the
movements of the orb with the binoculars. “Short bit left and then
out!” - Snare 13.6
↑Echidna materialized out of the darkness the Grue had created. She was
nearly twice the height she’d been before, to the point that the human
body on the top was miniscule, a speck by comparison. A human figure
atop a broad three-story building. - Scourge 19.4
“Marissa!” Echidna screamed, her voice guttural, voiced from five
different mouths. “Mars! It’s too soon! I want to kill them! I want
to kill them all! Kill this world! Destroy this universe that did this
to me! Not yet, Mars!”
The sun flew forward, melting pavement as it traveled, before it enveloped Echidna, Alexandria and the prison of ice and stone.
It hung there for nearly a minute, deafening with its sizzling and crackling. - Scourge 19.7
↑Sundancer created her flaming ball – small, but still far too bright to
look at – and sent it after Kid Win. The young hero scrambled for
cover, dropping his gun in his hurry to get away from the superheated
orb. - Sentinel 9.3
↑A few seconds later, Tattletale was back on the phone, “Genesis is
already making a body that can withstand the fire. Sundancer thinks she
can clear away some of the blaze by flash-burning the oxygen from the
area and drawing the heat and flame into her sun. If she can, it might
give us some elbow room.” - Prey 14.5
↑“There’s other limitations or advantages that come with the powers.
Sundancer over there can’t be burned. Temperature completely and one
hundred percent normalizes within a certain range of her body." - Scourge 19.3