Mago

"A Khal who takes orders from a foreign whore is no Khal."

- Mago to Drogo

Mago is a recurring character in the first season. He is played by stunt performer Ivailo Dimitrov and debuts in "Winter is Coming". Mago is a rider in Khal Drogo's khalasar.

Season 1
Mago attends Drogo's wedding to the Westerosi exile Daenerys Targaryen. He watches as two warriors squabble over a dancer at the wedding.

Mago objects to Daenerys intervening and refusing to allow the Dothraki to take their share of the Lhazareen women as spoils of war. He refuses to recognize her authority as khaleesi, calling her a foreign whore, and also defies Drogo. The Khal fights him, disdainfully disarming himself and deliberately accepting an arakh wound to show contempt for Mago's combat skills before slitting his throat with his own weapon and then pulling his tongue out through the neck wound.

Shortly after Mago's death, the wound he gave Drogo festers, leading to Drogo's death. Thus, technically Mago is partially responsible for Drogo's death.

In the books
In the A Song of Ice and Fire novels, Mago is part of Khal Drogo's khalasar, serving under Ko Jhaqo. He complains that Daenerys deprived him of his rape victim, but does not defy Khal Drogo nor picks a fight with him. Drogo was injured not by Mago, but during a battle against other khalasar, by a bloodrider of the rival khal.

Following Drogo's death, Mago becomes a bloodrider for Jhaqo, one of the several Kos that proclaim themselves Khals, followed by a portion of Drogo's Khalasar. He seizes Eroeh, the Lhazareen girl that Daenerys saved earlier from him, then he and the other bloodriders gang-rape her, and finally cut her throat. When Daenerys hears about this, she swears that she will pay Mago back for what he did to Eroeh. So far she did not have a chance to fulfill her oath.

In the DVD commentary for the episode "The Pointy End", George R.R. Martin comments on the "butterfly effect" created when a character is killed off in the TV series, given that Mago continues to appear in the books.