From Destiny 2 Wiki
Ancient's Haunt is a Lost Sector in The Tangle.
Jump down from the cliff, summon the sparrow, and go left. Take the first turn right and you will come to The Tangle. Follow the right path and you will soon see a lost sector sign next to the cave on your right. Keep descending down and you will come to the Ancient's Haunt. The place will be crawling with Vex, so focus on taking down Minotaur and then switch to Goblins. Keep pushing, and you will soon come to another Minotaur, which will be guarding Pakrion. It's now a good time to activate your Super and eliminate him quickly. Continue going up, killing Hobgoblins and you will soon reach the chest.