After you have defeated Samuel's DK rangers, you will find 2 keys in his lair => one leads to the smith's forge, the other one to a door leading to the exit. Forge and placing a bomb in there gives XP, leaving via key not. Both lead to Act 2. Kiya
You are nearing the end of act 1 now. There are 2 levels in the citadel you have to get through. There is an island at the start of act 2 you will need to explore before getting to an imp village, after which head north west to find the teleporter stones.