Pool of Radiance is a relatively non linear game in which you can complete most missions at any point of the game. In theory you could arrive in New Phlan and walk directly to the castle and beat the final boss but in practice there is no way your party would have the equipment and experience to make this possible. The order that this walkthrough is presented in is a guide only but at low levels it is recommended you don’t deviate too far from it as the game will not be forgiving.
There are two maps that are important to use whilst exploring. The first is the map of Phlan itself which is split into blocks which you transition between by leaving the adjacent area in the appropriate direction or by catching a boat to the bay for those on the other side of the river. See the relevant page for a detailed overview of each city block in the suggested order of exploration.
Next is the overland map that you have access to once you leave Phlan allowing you to explore the surrounding area. Whilst in this map you can have a wide variety of encounters which can be friendly or hostile depending on your reaction. You can also find small random maps to explore which whilst interesting won’t yield any unique items.
Silver Dragon Cave
Near the source of the river a silver dragon lives in a cave if your party is friendly he will give you the quest to retrieve a magic bottle from the Kobold Cave. After returning to him he will advise you that it contains an Efreet that will help you fight the vampire who is the leader of the undead in Valhingen Graveyard. Any attempt to attack him will result in significant damage to your party as the dragon breaths on you before flying away.