Creation:

Isca the Unbeaten first appeared in X-Men #12 - Amenth, she was created by Jonathan Hickman and Pepe Larraz for the X of Swords event.

Origin:

Isca is the sister of Genesis and thereby sister-in-law to Apocalypse, and aunt to their children - Death, War, Famine and Pestilence. When the mutants of Okkara warred with the Amenthi Demons. Isca sensing that Okkara was doomed, her powers compelled to defect forcing her to spend over a thousand years fighting against her people and family.

Millennials later Annihilation ordered Isca to send a message to her sister that she could save Arakko if she defeated the dark god in a duel to the death. The offer was a trap. Genesis won the duel, but realized that she would be condemned to take up the Golden Helm of Annihilation and merge with the dark god, leading to Arakko's final defeat and its subjugation under Amenth. This allowed Isca to reunite with her family and their people, as they all now fought for Annihilation and Amenth.

X of Swords

Isca joined the Swordbearers of Arakko to fight against Swordbearers of Krakoa in the Tournament of Swords. At an introductory banquet she got along well with opposition such as Cable, Gorgon and Magik.

Isca fought against Betsy Braddock - Captain Britain was declared the winner when Betsy's sword and body shattered into pieces due to a spell Saturnyne had previously casted. Isca took part in various other challenges all of which she won.

However, Krakoa managed to close the gap, and won the final tie-breaking challenge, which caused Annihilation to summon all of her army to conquer Krakoa once and for all. Although victory seemed assured, the Krakoan swordbearers were soon joined by the reformedX-Men and Captain Britain Corps, turning the tide against Amenth. Isca's powers compelled her to defect to Krakoa's side.

A.X.E.: Judgment Day

When the Eternals, led by Druig, declared war on mutants, he sent Uranos Arakko to keep them from intervening on Krakoa. Once again compelled by her powers, the arrival of Uranos prompted Isca to switch sides immediately beheading Idyll, a fellow member of the Great Ring. Krakoan mutant Nightcrawler removed her from the battlefield, teleporting her in the ocean where Sobunar of the Depths kept her tied up fighting the creatures under his command.

The Great Ring and Brotherhood of Arakko managed to defeat Uranos and armory. With the battle concluded, the Great Ring confronted a defiant Isca. In order to defuse the situation, the Fisher King, head of the Table of Night, challenged Isca to a contest of understanding, with the winner being the one who truly understood the meaning of loss. Though Isca had never lost since the manifestation of her mutant powers, the challenge granted her an understanding of loss. Realizing her mistakes and that she did not belong among the Arakki, she renounced her place on the Great Ring and left Arakko, warning the others not to follow her.

Arakki Civil War

When Isca's sister Genesis returned to Arakko under the influence of Annihilation she launched a civil war. as Arakko split between those loyal to Genesis and the corrupting influence of Annihilation, and those loyal to Storm and the other members of the Great Ring who fought to preserve the new Arakko.

Isca remained neutral, claiming the mountains of Olympus Mons and Tharsis Montes as her domain, killing any who intruded upon her solitude, no matter their allegiance but granting refuge to those fleeing the war.

Powers

Never Losing: Isca's Omega-level mutant ability is that she never loses at any endeavor she engages in. Isca seem to posses a level of intuited aptitude as her can seemly learn any skill well enough to surpass her opponent. There is no challenge, wager or contest that she will not prevail in, whether it is a game of chance or a war. In contests of chance, probability is manipulated in Isca favor. However, this does not necessarily mean that whatever side she is on is guaranteed to prevail - if the odds against her team are stacked too high, her power seems to take control of her and forces her to switch sides. This is demoralizing for her original team, as Isca turning means that their defeat is guaranteed.

The nature of Isca's power suggests that her level of free will is somewhat limited, as her power may block her from following any path that could lead to her defeat, even if she wants to. When the armies of Amenth became too strong for the mutants of Okkara to hold back, Isca's power forced her to defect to Amenth against her will, thus betraying her sister Genesis.

Isca's mutant ability cannot be shut off much to her detriment as it has robbed of many life experience.

Immortality: Isca is extremely long-lived, as she is thousands of years old however she claims not to be immortal as there is "Victory in death".