This is the article where I brainstorm a number of different possible climaxes - which I referred to as endings to cut down on the number of inadvertent double entendres. I realised in the Comments section of the last article that when the word 'ending' is a loaded word and that my particular use of it is more in keeping with the term 'climax' and so I will actually start using it occasionally. I'm talking about the grand finale, rather than the Ending which covers everything from the final build up to the finale to the aftermath which is far more difficult to plot out and generally is best left open. Bear in mind that these don't have to be for the end of a campaign. They could be simply major highlights at the end of adventures during long running campaigns.
Perhaps the players might need to transport an important cargo by a specified time. Examples: Returning a kidnapped princess or information on her whereabouts to her father before he declares war. Bringing much-needed medical supplies to a clinic to save a loved one or perhaps bringing a dying loved one to a medical clinic. Transporting food to a besieged populace to prevent a surrender (or a riot). Or the more obvious delivery of weapons, armour, or fuel before a battle. The climax would involve the final obstruction and this need not be based around combat. It could involve a cratered section of road, a burning building, swimming through a submerged series of pipes, a mine field, a damaged wing, or maintaining consciousness while the air runs low. Try to think up something that requires multiple rolls using multiple skills (a burning building might require Stamina + Resolve rolls, Athletics rolls, Survival rolls, and Strength rolls) or a number of smaller solutions so that it runs similarly to a combat rather than hinging on a single die roll.
Perhaps the players must need to fight their enemy to stop a certain outcome. This could involve a straight fight between them and the enemy but it doesn't have to be. It could revolve around an ambush of superior numbers (in which case much of the effort is around setting up and the actual ambush may be over quickly). It could involve knocking out the enemy or taking them prisoner (again, most of the action might involve preparation such as if a sheriff kicks in the target's door while they're naked in the bath). It could be an assassination - perhaps sniping a sorcerer before a nasty ritual is completed (the major effort could again be preparation in getting into position OR it might involve a shoot out with the cult). It could be an old-fashioned cover-based shoot out or a stand up fight directly between the player characters and the enemy.
Perhaps the players need to kill someone but they don't need to combat it. This might even include vehicular murder such as running them down in a car, crashing a helicopter into the cult or driving a petrol tanker into the monster. It might involve setting explosives and then blowing something up from a distance. It could involve convincing a computer to trigger a security system against your enemy or perhaps you route poison gas through the air vents. Technology and traps are your friend here.
Perhaps the players need to protect something from an assault. They might have to repel thieves or killers by setting up their own security system and then get to watch the defences spring into action and make the buildings' rolls against a set of enemies. It might be fun for them to get to be like the enemies they so often have to face and so long as they get to make the rolls it shouldn't be dull at all for them.
Perhaps the players need to get information from a person. They might need to trick a defendant into implicating himself in a court (vampire, legal, whatever). Or get a courtier to have a politically unsavoury outburst in front of the king. Or torture information out of an enemy that will change the direction of an army. Or honey trap a bad guy into making the right sort of pillow talk with a microphone nearby. Or goad a villain into boasting about their plans. Whatever it is, it needs to be definitive and solve the major threat facing the players or it will just be another action rather than the main event.
Perhaps the players need to get information from a place. The computer needs to be hacked but there is a system admin on the other side. The code needs to be found and broken in a thrilling few minutes of letter substitution code breaking that the players themselves have to undergo (some people would love that sort of thing). Your best bet here is to set a time limit and, again, make the results definitively important.
Perhaps the players need to deal with a particular trap that is important enough that the story hinges around it. An obvious example would be defusing an Unexploded Bomb in a British Home Front situation or a bomb left in an airport in a modern day scenario.
Perhaps the players need to build a case. The final crime scene has the clues that will get the enemy apprehended. The lab is so close to proving that a hurricane is about to hit and they need to put forward a case that the other information is false misinformation sent by an enemy state happy to have so many killed during a parade. Once the case is made, the threat is solved. The enemy is thrown behind bars. The parade is called off. You also have to make it obvious that this is the definitive encounter to build up the tension - some genres will make this automatic (i.e. police procedurals).
Perhaps the players need to talk someone down. They have all the information they need and just need to defuse the situation with the hostage taker. Or perhaps they need to talk down the suicidal informant from a ledge. Or they need to convince someone that they don't need to kill their enemies and should let the law handle it. Or perhaps they need to be convinced not to declare war or place an embargo on another country or call down martial law. Whatever it is, it needs to be important in the perspective of the story at hand. A game based on Historical Drama might simply be able convincing a man not to undertake a duel or abandon his wife while a game based on Global Superheroes might talk down Dr. Megalomania from using his Destructobeam that would blow up the world and him with it.
Perhaps they need to use a certain technology (magical or scientific) themselves. It might be accurately using all of the ingredients so far gathered in a ritual to banish an enemy or using an exorcism while surviving a ghost's attacks. It could be that they need to repair an aircraft so they can get off the island or cleverly manipulate the various energy systems on a spacecraft so that life support stays on a little longer.
Perhaps they need to steal something, ideally without even being spotted. They may have to avoid traps, security systems, roaming dogs, cameras, and patrolling sentries on the way in and, more difficultly, getting out without the missing item being noticed. Throw in a final complication that should be difficult to surmount but take care not to let all their effort disappear in a single die roll. Perhaps have that failed stealth roll simply make things harder when the enemy is now on alert and has changed up their search patterns. Or perhaps that failed Spot Hidden doesn't mean they step out in front of the enemy but they get lost in the building and have to find their way out. Each failed roll should generally simply move them further away from the objective as statistically they're bound to fail the occasional roll (1 in 20, at the very least, in Pathfinder or D&D).
If you make a failed roll, almost any failed roll, a guaranteed Lose The Mission roll then you've just invalidated all their previous effort and made such stealth operations impossible. Luck should influence a stealth mission but not rule it. If it's a super-important die roll or if the players have been profoundly stupid and you've given them a die roll to see if they can pull it off, then go right ahead. Otherwise, try to have it be a series of bad rolls / bad decisions that auto-fail the mission and even then its best to have them be consecutive failures. Anything else can just add further complications and therefore simply ratchet up tension.
So, do you have any other ideas of main ways of ending the plot?
The main Endings article (and all the various links) can be found over here.