Origin Earth 712
Arcanna of Earth-712 originally worked as a medium before becoming a professional crime fighter who captured criminals for profit. Phillip Jones, her husband, stayed home to raise their children Drusilla, Katrina and Andrew. She later accepted an offer of membership into the Squadron Supreme, making her the fifth recruit.
Arcanna was created by JM De Matteis and Don Perlin and first appeared as a new member of the Squadron Supreme in Defenders #112 in October 1982. Her character (as do the other Squadron Supreme team members) parallels a DC Universe character - in this case, Zatanna.
Major Story Arcs Earth-712
Later on Arcanna became pregnant again. Fearing that others would find out and detain her from duties and in battle, she concealed it through an illusionary spell. She and her family later moved out of their secret house located in the woods into Squadron City with the rest of the other families of the Squadron Supreme, as she used her same illusion power to conceal it. During a battle led by Nighthawk's rebel team of Redeemers, she faced off against Moonglow. At that crucial moment she went into labor. At the end of battle she gave birth to a boy name Benjamin Thomas Jones.
When Earth-712 was threatened with destruction by the Nth Man following the events of the Utopia Program, Power Princess told Arcanna to stay behind due to her recently giving birth. However, Moonglow who feared to go on the mission and allowed Arcanna to switched places with her in order to go on the mission into space. During the last moments, Arcanna reveals her true identity to Power Princess who is glad that she gets to die with someone she likes. Before their death can happen, Arcanna's infant son Benjamin sacrifices himself to save the team and his mother, which leads him to switch place with the Nth Man, causing his mother to burst into tears. The team is banished as a result to the mainstream Marvel Universe following these events, and Arcanna appears as Moonglow when the team encounter the Avengers and Quasar.
Arcanna and the other members returned back to their own universe with the help of Iron Man, but their world had changed, and was now under the control of the Global Directorate. Arcanna returned home to inform her family that their son had sacrificed himself to save that universe. Nth Man who was now known as Mysterium contacted her and told her to stay home with her family as the Squadron Supreme was going down a road in which they would be without her, also due to her having to retrain her magic since the magic in her originally had changed.
Arcanna retired from adventuring and stayed with her family until the Ultimate power crossover. Scarlet Witch from the Ultimate Universe used her hex abilities on the Squadron Supreme of Earth 31916, causing the Squadron from Earth 712 to appear and fight their counterparts. With the help of two Arcannas, Scarlet Witch restored everyone back to their respective universes.
Origin Earth 31916
Though not expressly stated, it is highly likely that Arcanna gained her abilities as a result of the nanovirus that came to Earth on Hyperion's ship, that is also responsible for giving many other humans powers in that universe (Earth 31916).
Arcanna has not been fleshed out as much as some of the others in the JMS revamp of Squadron Supreme. She was the author of a book on quantum physics before she was first recruited. Before the Squadron was officially started, she was a member of a smaller team (Shape, Mr. Gaines, Emil Burbank, and herself) that was sent by the General who created the Squadron, to retrieve Hyperion and bring him back under the governments control. During a freak accident resulting from her powers meeting with Hyperions flash vision, and Mr. Gaines radiation bursts, they were all sent into the future for a short time. Once Hyperion was back, she became a founding member of the Squadron Supreme.
The first Arcanna had formidable magical powers. She can use her magic to control the elements of nature, earth, air, fire, and water, this also extended to metal which was limited. She was also able to use her spells to create illusions in which she did multiple times especially to conceal her pregnancy. With her powers she can fly by using the winds to carry her through the sky or a broomstick which she used earlier on but discarded it. She also posses mythical senses which allows her to feel the magical phenomenal events and know the magic of a universe she is on. The downfall to her magic was that it only had effect on natural substances, except her magical force blast. She was an expert in magic.
She is a fair hand-to-hand combatant, having received coaching from Nighthawk and Power Princess.
The second Arcanna controls quantum outcomes. She sees all possible quantum realities and is able to choose which one happens, allowing her to manipulate probabilities. With this she is seen shifting guards guns into a large glass of beer, turning a small pebble into a bird, creating birds to cushion Nick Fury's fall, and among other things. She had no limits to her power, due to it being able to control probabilities. Her powers was equally match to Scarlet Witch of the Ultimate Universe, which means she was indeed powerful. She is also a leading expert in quantum mechanics due to this ability. Her main limitation was that using her power too much could result in the unraveling of the fabric of space-time.