Scepter

"You question us? You question HIM? He, who put the scepter in your hand, who gave you ancient knowledge and new purpose when you were cast out, defeated?"

- The Other to Loki

The Chitauri Scepter, also known as Loki's Scepter or Loki's Staff, is a scepter that utilizes a blue gem powered by the Tesseract, similar to the HYDRA Cannon. It was wielded by Loki in the invasion of Earth, who received it as gift from Thanos.

History
"You've got the glow stick of destiny. Would you like a drink?"

- Tony Stark to Loki

The Chitauri Scepter, a powerful artifact with ties to the Tesseract, was entrusted to Loki of Asgard by the tyrant Thanos, along with an army of Chitauri warriors, under the condition that Loki travel to Earth to secure the Tesseract itself and prepare the Earth for subjugation under his rule. Loki arrived on Earth through a portal jump-started by the Tesseract, arriving in the Joint Dark Energy Mission Facility, and used to scepter to quickly defeat a unit of armed S.H.I.E.L.D. agents that were present. Loki proceeded to use the scepter's powers to control the minds of agent Clint Barton and scientist Erik Selvig before escaping the facility.

Loki continued to carry the scepter during his activities on Earth, using it to establish a mental link to speak with The Other, and using it during several altercations with The Avengers. After being captured and imprisoned on S.H.I.E.L.D.'s Helicarrier, the scepter was stored in a science lab on board, where it was observed and studied by Tony Stark and Bruce Banner. During an argument among the Avengers members and Nick Fury, the scepter was revealed to be slowly affecting their minds, increasing tensions and turning them against each other until an immediate threat put them back in focus.

Upon escaping from his holding cell on the Helicarrier, Loki regained the scepter, which he later used to stab agent Phil Coulson through the heart when Coulson attempted to stand against him. Loki continued using the scepter to fight against the Avengers in New York after opening a portal for the Chitauri to invade Earth, until he lost it shortly after fighting his brother Thor. Near the end of the battle the scepter was picked up by Black Widow and used to activate a fail-safe that closed the portal being generated by the Tesseract.

Following the invasion, Black Widow turned possession of the scepter over to S.H.I.E.L.D.

Some time after, HYDRA sleeper agents working in S.H.I.E.L.D managed to pass the scepter onto Wolfgang von Strucker whose scientists begin to study it, realizing that no one truly understood the power of the scepter.

Capabilities
"What we have is more than any of them ever knew. We've only scratched the surface."

- Wolfgang von Strucker on the scepter's power

The scepter, in its main form, has a golden handle and a black fitting which holds a blue gem encircled with silver blades. It allows its owner to open rifts through dimensions using the Tesseract as a gate key, fire powerfully destructive blast of blue energy, communicate across space through a form of astral projection, and bend the will of others by controlling their hearts.

The Scepter can be transformed at will by its user, changing between at least three distinctly different forms. In its main form, the scepter has two blades encircling its blue gem, an elongated blade over the gem and a shortened blade underneath, as well as having a shortened handle, measuring approximately two feet in length overall, making it ideal for close-quarters melee and firing accurate energy bursts. When carrying it into battle the scepter can be transformed into a spear-like form with a much longer handle, lengthening to approximately six feet, and more pronounced blades, including an additional pronounced blade underneath the gem. In some situations the scepter can even be disguised as an ornate walking cane, approximately three feet in length, taking on a strait, slender appearance, removing the blades and leaving the blue gem as an ornament to give it a regal appearance.

The scepter functions as a formidable weapon, its sharp blades being able to violently impale and slash enemies, besting most in combat with ease. It is made from extremely durable materials as it was even strong enough to match Thor's mighty hammer Mjølnir in close-quarters combat.

When using the scepter to control another person the user places the blade tip against the person’s heart and the gem produces a blue, wisp-like energy which is transferred into the person’s body where it the spreads up to their head, notably affecting their eyes, turning them a florescent blue color. People put under the scepter's control will often regain their individuality after receiving a significant blow to the head, as a temporary loss of consciousness will allow their normal mental state to "reset" and return. In some situations the effects of the mind control can be negated outright if the energy from the scepter is unable to diffuse into the target's body, such as when Tony Stark's Arc Reactor absorbed the energy instead.

Loki has also used the scepter to mentally communicate with The Other using a form of astral projection that allowed him to experience the conversation as if he were in the Other's presence, even across space. During this conversation The Other was able to cause Loki pain through the scepter.

Trivia

 * Due to the appearence of Thanos as well as the scepter's ability to control the minds of others, fans have speculated that the blue crystal on the chitauri scepter is the Mind crystal from the Infinity Gauntlet.