One quest line you can pursue is the Royal Lineage. Working on the assumption that a royal line is a factual thing, via DNA etc, then I have assumed that certain magical items of power have been linked to that royal line. This is the rationale for why the Shadows want to kill off the royal line, to remove the very powerful artifacts that are available to it, and might be used against the Shadows.
As part of the story line one of the players can be the last royal heir, or if none of them wish to play the role then the party inherits a 16 year boy during their escape from Castle Bord who is the son of the King. It will be better if a player takes on the role.
The items that can be used are as follows:
The Belt - immunity to disease and poisons.
The Crown - Protection vs Elelmental damage
The Sceptre - Heal
The Ring - Spell reflection/resistance
The Scabbard - Improved Leadership
The Sword - bane vs Shadows and Undead
The Shield - immunity to Fear
The Standard - improved morale, light.
Each item should have a specific power, and they should gain extra powers as they collect more items (a set). Extra powers can be generated from the following list, one new power for each item over one gained:
+1 HPs for party
+1 to all attacks
+1 to all damage
+1 to all skill rolls
+1 to save throws.
-1 to all incoming damage
+1 to initiative rolls.
At game start the heir will only have one of the items, whilst another member of the party will have another. In the original game they had the Belt (the heir) and the Standard (the bodyguard).
The remaining items will be scattered all over the place, and need to be tracked down and recovered. As artifacts they cannot be destroyed except if the entire Royal Line is killed. The fact that they remain tells the Shadows that someone escaped, and they will be looking for him/her.
The Bodyguard - one of your players can become the Bodyguard, you are the sworn hereditary protector of the King, your family has held this role for 50 generations and it is now breed into your DNA. You are so closely related to the royal line that you are able to use the Standard, which you would normally hold in battle.