Here is how I would structure the Necromancer scenario in order to avoid the problems of railroading and illusionism (which I do consider to be a problem):
The basic scenario is that a Necromancer is raising an army of undead in order to attack a town. There are opportunities for the PCs to prevent the necromancer from raising undead for his army, but the PCs can easily miss these opportunities or ignore them in favor of other choices, such as bolstering the town's defenses in preparation for the attack.
Now then, if the PCs have the opportunity to weaken the Necromancer's forces beforehand, then I want their actions to have real meaning. Let's say that there are three opportunities for the PCs to weaken the Necro's forces: preventing his minions from raising grunts in a graveyard, preventing him from creating a powerful undead monster, and a chance to prevent some thieves from stealing bones from an underground crypt.
Now then, in the second case, I would create a specific monster, probably a strong elite or solo type monster. If the party doesn't stop it from being created, it will be there in the final battle. If the party does destroy it early, then it will probably be replaced by weaker minion or regular type monsters.
In the third case, if the Necromancer's minion's succeed, then the Necromancer's forces later on will be bolstered by relatively strong skeleton type undead. If the first case, the Necromancer's forces will be bolstered by relatively strong zombies. If either of these fail, the Necromancer's overall army later in the campaign will be much smaller.
Now then, if the PCs successfully prevent two or three of the Necromancer's plans, the Necromancer may actually abandon his plot and flee the area. The PCs will then have the choice of pursuing him or leaving the area themselves in order to follow up other story threads. The Necromancer may or may not resurface in the campaign, depending on other events.
If the PC's do not prevent the Necromancer's plans, the Necromancer will lead an attack on the community. How the battle goes specifically depends heavily on which forces the Necromancer has and what kind of preparations the PC's made for the town's defense. In any event, the attack will probably be a big multi-encounter sequence where the PCs have to decide between trying to hold the city gates against an undead behemoth and trying to stop a force of skeletons from scaling the city walls elsewhere (as examples). Conceivably, the enemy might overwhelm the PCs and destroy the city, forcing the PCs to retreat. Alternatively, the Necromancer's weakened forces may be devastated by the PC's carefully planned defenses, leaving the Necromancer himself vulnerable to a vicious counter-attack.
I think it relatively simple to fill a scenario like this with meaningful choices as long as you don't lock your thinking in to any particular outcome. Who says that the PCs will ever fight the Necromancer head on? While it is certainly a possibility that can be achieved in a number of ways, there are so many other ways the battle can play out.
Now then, a scenario like this is not sandbox play in the least. It is following a plot-line of sorts, and will eventually come to one conclusion or another. At the same time, it is not really railroading, as long as the DM lets the PC's decisions shape the scenario's course and outcome.
The basic scenario is that a Necromancer is raising an army of undead in order to attack a town. There are opportunities for the PCs to prevent the necromancer from raising undead for his army, but the PCs can easily miss these opportunities or ignore them in favor of other choices, such as bolstering the town's defenses in preparation for the attack.
Now then, if the PCs have the opportunity to weaken the Necromancer's forces beforehand, then I want their actions to have real meaning. Let's say that there are three opportunities for the PCs to weaken the Necro's forces: preventing his minions from raising grunts in a graveyard, preventing him from creating a powerful undead monster, and a chance to prevent some thieves from stealing bones from an underground crypt.
Now then, in the second case, I would create a specific monster, probably a strong elite or solo type monster. If the party doesn't stop it from being created, it will be there in the final battle. If the party does destroy it early, then it will probably be replaced by weaker minion or regular type monsters.
In the third case, if the Necromancer's minion's succeed, then the Necromancer's forces later on will be bolstered by relatively strong skeleton type undead. If the first case, the Necromancer's forces will be bolstered by relatively strong zombies. If either of these fail, the Necromancer's overall army later in the campaign will be much smaller.
Now then, if the PCs successfully prevent two or three of the Necromancer's plans, the Necromancer may actually abandon his plot and flee the area. The PCs will then have the choice of pursuing him or leaving the area themselves in order to follow up other story threads. The Necromancer may or may not resurface in the campaign, depending on other events.
If the PC's do not prevent the Necromancer's plans, the Necromancer will lead an attack on the community. How the battle goes specifically depends heavily on which forces the Necromancer has and what kind of preparations the PC's made for the town's defense. In any event, the attack will probably be a big multi-encounter sequence where the PCs have to decide between trying to hold the city gates against an undead behemoth and trying to stop a force of skeletons from scaling the city walls elsewhere (as examples). Conceivably, the enemy might overwhelm the PCs and destroy the city, forcing the PCs to retreat. Alternatively, the Necromancer's weakened forces may be devastated by the PC's carefully planned defenses, leaving the Necromancer himself vulnerable to a vicious counter-attack.
I think it relatively simple to fill a scenario like this with meaningful choices as long as you don't lock your thinking in to any particular outcome. Who says that the PCs will ever fight the Necromancer head on? While it is certainly a possibility that can be achieved in a number of ways, there are so many other ways the battle can play out.
Now then, a scenario like this is not sandbox play in the least. It is following a plot-line of sorts, and will eventually come to one conclusion or another. At the same time, it is not really railroading, as long as the DM lets the PC's decisions shape the scenario's course and outcome.