The Scepter of Darkness is a sceptre-like artifact with dark powers and an object in Sonic the Hedgehog (2006). It was originally designed as an emergency measure during the failed time research program known as the Solaris Project (named after the Kingdom of Soleanna's ancient patron solar deity), and its purpose was to contain the demonic entity called Mephiles the Dark.
Some time before the events of the game, Mephiles was sealed away inside the Scepter of Darkness by a time-traveling Shadow, which was given to him by the dying Duke of Soleanna which founded the Solaris Project in his wish for his people and all of humanity to rewrite their past mistakes, and in his desire to see his deceased wife again, by studying and using the time-warping power of his god Soloaris. However, he left it out in the open, citing that he "knows what will happen to it anyway.".
It eventually came into the possession of the mad scientist Doctor Eggman, and the flamboyant treasure hunter Rouge was sent by the G.U.N. government to steal it from him. Shadow (before he had traveled back in time) went to rescue Rouge and during their escape, Eggman attacked the duo in hopes of reclaiming the scepter. After a struggle between the three, the scepter was broken, which released Mephiles.
Some time later, Shadow and Rouge came across an archaeologist named Adrianna who was studying the scepter, and after saving her from an attack by the minions of the destructive fire spirit called Iblis, she read to them an ancient text she discovered about the scepter and Mephiles, although she was unable to comprehend its meaning. After that, the two constructed a new Scepter of Darkness in hopes that they could re-imprison Mephiles. Unfortunately this new scepter could never seal Mephiles because he had grown too powerful from the Chaos Emeralds, combined with the present Mephiles absorbing the shade of Shadow the Hedgehog when he was freed and was destroyed in the attempt.