Harrison Jones appears as one of several daily npcs who can visit your garrison. He will offer six quests as part of the Master Relic Hunter achievement.
The Silent Skull: The Infected Orc
Fly to Everbloom Overlook in Gorgrond and kill Enthralled Mutants and Twisted Guardians for the Journal.
The First Reagent
Fly to Everbloom Wilds to find the Shadethistle Leaves under some rock formations.
The Second Reagent
Fly back to Everbloom Overlook and loot the Bonethorn Vine off some nearby bones.
The Third Reagent
Travel past the hydra pools and steam vents in the upper part of Everbloom Wilds to locate the Steamcap Mushrooms.
Taking from the Taker
Enter the nearby cave to brew and drink the elixir. This will allow you to talk to the Brightscale Ravager at the cave entrance who will lead you to Skulltaker. Be sure to avoid any skulls and their auras (just like the Timeless Isle cave for Zarhym Altogether). Kill Skulltaker and collect his Silent Skull. Hearth back to the Garrison.
Hand the quest into Rokhan for your 150G reward.