How do I complete the Old Goat quest in Goat MMO Simulator?

I know where Old Mountain is. I know how to get him. But how do I complete the quest if I cannot bring items in my inventory over to Goatwind? There is no good explanation online for doing this.

I am running the mobile version on Android.

The Old Goat achievement is obtainable by going through the portal in the Entrance and getting through every trap to get to his room, where you them must "kill" him to get the achievement. I'm writing from the perspective of a PC Player, so if it doesn't work, I apologise. I will go through the game on mobile and give you a better explanation if there's anything different to the PC by getting that achievement.

EDIT 1: You only need to enter his room, not kill him. That is a quest, not an achievement. Sorry.