Artanis is the player's character in the original Starcraft. Artanis is a gifted Templar, rising to the rank of Executor at the age of 262 (extremely young for a Protoss). Artanis commanded the Protoss armies for the Conclave. Along with his comrade, Fenix, Artanis launched many successful campaigns against the Zerg.
In light of his successes, the Conclave sent Artanis to capture former Executor Tassadar, the Executor that Artanis replaced. Upon meeting Tassadar, Artanis was compelled to abandon the Conclave to help Tassadar with his mission of reuniting with the Dark Templar. The Dark Templar wielded the mystical energies of the Void, capable of slaying the Zerg Cerebrates. Battling through Zerg and Terran forces, Artanis and Tassadar unite with Zeratul and his Dark Templar and together they returned to Aiur. They were immediately ambushed by Protoss forces under the Conclave's command; the Conclave has branded Tassadar as a traitor and has ordered the Dark Templar to be handed over for execution. After fierce fighting, Tassadar surrenders himself to the Conclave. WIthout Tassadar, the Dark Templar vanish, leaving Artanis and Fenix to fend for themselves.
Thankfully with the help of Jim Raynor and his Battlecruiser, Hyperion, Artanis was able to rescue Tassadar before his execution. With Tassadar's return, so too does Zeratul's. Zeratul shares his vast knowledge of the Zerg swarms, culminating in a final assault on the Overmind. Despite the combined Protoss and Terran armies, the Overmind remains alive and prompts Tassadar to sacrifice himself to destroy the Overmind once and for all.
With the destruction of the Overmind and feral Zerg rampant on Aiur, Artanis guided the surviving Protoss to the Dark Templar homeworld, Shakuras. Unfortunately, the Zerg also follow. Under advice from a reformed Kerrigan, the Protoss obtain the Uraj and Khalis crystals necessary for the activation of the Xel'Naga Temple and the complete purge of the Zerg. Though successfully activating the temple, the victory came at a heavy price. Aldaris, head of the Conclave, was slain by Kerrigan and Kerrigan revealed that she was using the Protoss for her own personal gain. Artanis was separated from Zeratul after the temple activation. He led the Protoss forces in a final desperate attempt to kill Kerrigan alongside the United Earth Directorate and the Terran Dominion. The attack was failure and Artanis and his forces retreat to Shakuras to rebuild the Protoss civilization.
Artanis makes a brief cameo in Starcraft II: Wings of Liberty. It is revealed that Artanis has been named Hierarch, the leader of the surviving Protoss. In a mission meant to represent a potential future if Sarah Kerrigan was killed, Artanis, onboard a mighty Protoss Mothership, joined the last of the Protoss race in an ultimately futile defence against a Zerg swarm lead by "the Fallen One", who apparently is a Xel'Naga. By the end of this theoretical mission, Artanis, along with Zeratul, Selendis, and all the rest of the Protoss, were killed by the never ending waves of Zerg and Zerg/Protoss hybrids. In his "death", Artanis expresses regret that he couldn't see Kerrigan as the savior of the galaxy. The player experiences this mission in the form of a vision of the future glimpsed by the late Zerg Overmind, which was shown to Zeratul by the spirit of Tassadar, and finally shown by Zeratul to Jim Raynor, the protagonist of Wings of Liberty. Assuming he doesn't die in Heart of the Swarm, Artanis will likely play an important role in Legacy of the Void, possibly helping Zeratul reunite the Protoss.
The name "Artanis" was supposedly created when developers were sitting around listening to Frank Sinatra albums thinking of names for their characters. Exhausted from a day of work, they decided to just use Sinatra's name backwards, creating "Artanis"
In his Brood War appearance, Artanis is seen half naked with shortened neural appendages, a trait of the Dark Templar. Blizzard admits this was a mistake and Artanis' appearance was corrected in Starcraft II.
Artanis: What do I look like, an Orc? This is not 'WarCraft in Space'! It's much more sophisticated!