If you read the "Story so far..." in the User Guide, you might assume the game ends with an epic battle with Granak. Your assumption is wrong. Instead the character learns about a legend of a hero who acquires the Amulet of Yurth and uses it's power to free the land from an evil oppressor. The game ends when the Amulet of Yurth is recovered.
As you may have noticed nothing is mentioned of the amulet in the intro. This is intentional. Unlike the Legend of Zelda, the character does not need to go around and get pieces of something before going to the end. Not all the dungeon levels are even required. Information and items are given in the various dungeons that could prove helpful. Some of the items may be required but not all.
The game was never intended to be cutting edge in terms of graphics. A higher quality graphics version is certainly a possibility for the future, however, levels, monsters and items are needed much more at present. Also the game should still be playable in a nostalgic 8-bit nintendoish graphics mode.
Other Background Info: Troll Bridge has been around as an idea of Dennis Payne for quite some time. Before the Zelda style game both a Rogue-like and Bard's Tale like games were thought of and sometimes partially implemented. Because of this, some ideas about the world of Troll Bridge may not be suitable to the Zelda style game.
The Troll Bridge world has no humans or at least they aren't a common race. Instead trolls are the dominate race. There are a variety of troll species. The hero of Troll Bridge and Granak are cave trolls. They are probably the most common. Two-headed trolls are the most savage and bestial of the trolls. Granak uses a lot of them in his army and as guards. Gray trolls are the wise mystics but were nearly wiped out by a plague a while ago. Water and black trolls also exist but are not for use in the current game.