HistoryDaylight was born from a sample of Twilight Sparkle's DNA, cloned and incubated into a same-age duplicate with the same personality but no long-term memory and a confused mindset. Then Doctor Nefarious placed her into a corruption machine that corrupts via mental simulations. Thus she is shown her DNA donor's life, and then introduced to a scenario where the Element of Magic is conflicted. She discovers that magic is tied to emotions and friendship is what makes her in particular powerful, and since nothing lasts forever, not even friendship, and she is shown all the conflicting events in Twilight's friendship, but a completely possible scenario where her friendship would fall beyond repair with Twilight trying to sacrifice the carefree loved nature of Equestria to promote her Friendship School and thus cause an uproar that destroys everyone's trust on her, she went through self-harm and corruption, and thus harnessed and mastered black and chaos magic, becoming convinced that magic was best used for power, swearing allegiance to Nefarious with her equally-corrupted clone friends into becoming the Elements of Disharmony, going by the name Darklight Spark, only as a ploy to betray him in the end and pursue a bigger goal.
As a reverse Twilight, she is incredibly ambitious, arrogant, and egomaniacal, much more than her creator, knowing everything about evil under the influence of corruption, wishing for all magic she can want for domination and ultimately betrays Nefarious to take over Equestria. She's also self-righteous, self-entitled, incredibly envious, proud, unrestrained, never gives up to the point of collapse, powerfully manipulative, helps to help herself and her evil friend circle, and even mocks her own DNA donor for being a valedictorian of magic and an intelligent person yet stupid enough to require friendship lessons, introverted and antisocial beginnings aside.
Daylight is as smart as her DNA donor if not more. She has Twilight's ability to learn a spell by seeing it in action, her memory is powerfully clear, and her magic is two times stronger than Twilight's. Like all Equestrian magic, her magical powers are tied to her emotions. She can do anything and everything Twilight can do, but she's also knowledgeable more in black magic as a result of her evil psychology, and even combined both light and dark magic to create bootleg Equinox magic which used to be unstable without full mental stability. She knows how to use chaos magic because of the torture used to turn her evil, granting her more unpredictable potential, and after mixing all three, she created her signature Triad Power, which is extremely unstable and has different effects and grants boosted power, but is extremely addictive and corruptive. With her Alicorn physiology, Daylight has the flight of a pegasus and the strength of an earth pony, and her magic is extremely powerful.
She used to be the sole caretaker of the Tree of Disharmony, created by Doctor Nefarious as a negative counterforce to the Elements of Harmony, which gave birth to the Elements of Disharmony, which are the reversed Elements of Harmony that she and her friends can wield, and just like the Harmony Element of Magic, the Disharmony Element of Magic is a power in it's own right. With this power, combined with the Tree of Disharmony's Monochrome Power, Darklight and her friends are equal in power and strength to the Mane Six. But since the Tree's destruction, she gained the same powers as Twilight including the ability to use the Element of Magic and the Rainbow Power.