He was on the road to Waterdeep to begin his apprenticeship, but he was attacked by goblins near Phandalin and had his kit stolen. He stopped in Phandalin after being robbed, and sulked at the Stonehill Inn where he briefly met Farryn Phirie.
After hearing that the goblins that had stolen his kit had been defeated, he left to go search for his equipment at the Cragmaw Hideout, but was captured by a returning scouting party and brought to Cragmaw Castle.
He was freed by The Party at the castle, and happened upon his tattoo kit in the goblins' kitchen while Gunter cooked the freed captives a meal. The goblins had tried using the magical ink as a cooking ingredient.
Back in Phandalin, Demetrius gave Gunter a magical tattoo as a reward for freeing him, and told the Party how to find him in Waterdeep.
When the party arrives in Waterdeep while following the Keepers' caravan, they stopped by Demetrius's place of work. His master was away, but Demetrius gladly tattooed the party, and gave them information about the city