High Priestess Mar'li

Mar'li was the high priestess of the spider loa, Shadra. Sent by King Rastakhan to Zul'Gurub to stop Hakkar the Soulflayer with the other loa high priests, she was corrupted by the blood god and had to be defeated at the Zandalari's behest. She somehow returned during the events of Mists of Pandaria as part of the Council of Elders, but was slain at the Throne of Thunder.

World of Warcraft
In order to quell Hakkar the Soulflayer, the trolls of the land banded together and sent a contingent of High Priests into the ancient city of Zul'Gurub. Each priest was a powerful champion of the Primal Gods, or loa, but despite their best efforts, they fell under the sway of Hakkar and were forced to channel power into the blood god. Ultimately, Mar'li and the other priests were slain by the adventurers who entered the city, along with Hakkar. She was thankful to be at last freed of the blood god's influence.

Mists of Pandaria
Mar'li had somehow returned, and served as the leader of the Gurubashi tribe in the Council of Elders at the Throne of Thunder.

Notes and trivia

 * Mar'li's belt buckle and shoulder pad resembles a spider mask, as a tie to Shadra.
 * Prior to the Throne of Thunder raid, Mar'li had likely been one of the Zandalari that were sent to Zul'Gurub. However for the Mists of Pandaria raid she was changed into a jungle troll and had become the leader of the Gurubashi tribe of jungle trolls.
 * The name of her model is "jungletrollcouncilor".

Speculation
It's possible that, like fellow priest Venoxis, she was resurrected by Jin'do and Zanzil, or that she didn't die at all.