Camp Crystal Lake is cursed, or at least that's what they say. Even since that kid drowned there, the place has been called Camp Blood. People keep winding up dead, and every time someone tries to re-open the thing, tragedy strikes. Most people don't even know about it now, but you still hear screams sometimes. Because murder lurks in those trees; a vengeance that will never truly be slaked, no matter how many people it eats.
The curse has a name, and it's name is Jason Voorhees.
This iconic slasher has carved his way through entire generations of teen campers who decided to sneak off into his woods. In fact, his onscreen body count numbers in the triple digits. If you'd like to bring the sort of killer the hockey-masked myth has become to your Pathfinder game, either as a player or as a DM, then this guide should help get you started.
Lastly, if you're looking for other slashers, superheroes, or famous fantasy figures like the Game of Thrones cast, the Character Conversion page on Improved Initiative has all that, and more.
Alternatively, if you'd like to look deeper into the reasons for Jason's popularity as a slasher, you might be interested in 5 Reasons Jason Voorhees is One Of The Greatest Slashers over on Horror Media.
Race, Attributes, and Traits
Jason Voorhees was born with severe birth defects, including facial deformities that made him the subject of ridicule. And though he would eventually rise from his grave, the Jason who initially stalked the woods around Camp Crystal Lake was very much human. Though, to enhance his strange legend, taking the alternate racial trait Dimdweller (+2 on Stealth, Intimidate, and Perception checks while in concealment caused by dim light or darkness, and darkvision to 60 feet) instead of Skilled. Also, though he was born with severe deformities, Jason grows into a towering figure. While his physical attributes are primary (with Strength and Constitution likely his two biggest stats), Wisdom and Charisma are mental stats worth investing in. Especially since he certainly has presence, even if he doesn't have looks.
When it comes to his traits, you need to choose options that are going to come into play with regularity. One of the most appropriate traits is Briar Bandit (+2 trait bonus on Stealth checks, and +1 trait bonus on sneak attacks in overgrown areas), though Blighted Physiology (+1 natural armor bonus, but you become sickened for 1 round any time you receive magical healing) could also represent Jason's unusual anatomy. Other traits include Sworn Enemy (choose a type of creature from the favored enemy list, and gain a +1 to damage against that kind of creature), Vengeful (+1 trait bonus on damage against any creature who has damaged you in the past 24 hours), and Reactionary (+2 trait bonus to Initiative checks) are also good options.
Everyone thought Jason had drowned when he was a boy, but he grew up as a mostly feral child hiding in the woods. He lived off the land when he could, and stole from the camp when he couldn't get enough on his own. A combination of woodscraft, determination, and sheer skill make the slayer a great choice for Jason. Not just any slayer, though, because thanks to Horror Adventures we now have the Bloody Jake archetype on page 66.
What does the Bloody Jake do? Well, it grants you favored terrain at first level (forest, naturally), and it gives you an ability called Cruel Tricks. These allow you to throw your voice as ventriloquism (which might explain the infamous ch, ch, ch, ah, ah, ah that follows victims), make opponents shaken, and get people lost in his favored terrain. You also gain the ability to build ranger traps, and at 13th level you can use tree stride once per day. Because appearing and disappearing nearly at will is what slashers in general, and Jason in particular, are known for. You won't get many Slayer Talents with this archetype, but taking the Rogue Talent to get Fast Stealth is definitely a good plan. When you gain access to Advanced Talents, Camouflage should be the first thing on your hit list.
For those who love mixing and matching, though, the formula gets even better if you take a 2-level dip in barbarian. The Dreadnought archetype (Horror Adventures 47) gives you half the bonuses of your Rage, but no negatives. You are also not fatigued after your Rage. You trade in fast movement, but in return you are harder to slow and stop. Smasher is the ideal Rage Power for this build, since it explains how Jason can slam his machete through a car door, or how even barricaded doors fall in a single blow.
Skills and Feats
Slayers get more skills than you'd think, and much like Jason, they have a lot more tricks up their sleeves than it might appear. The most obvious skills for Jason are Perception, Survival, Stealth, and Intimidate, though you might also want to include Craft and Acrobatics. Swim, for obvious reasons, likely shouldn't be on the list.
When it comes to Jason's feats, it's important to ask what sort of results you want. Because if you're going to be springing ambushes a lot of the time, then you'll want to take Power Attack, Furious Focus, and all the Vital Strike feats, as detailed in One Hit Wonders: Building a Bigger, Badder Brute. If you want to make use of all your Intimidate bonuses, then Cornugon Smash (Cheliax: Empire of Devils) is a feat you'll definitely want to have. Weapon Focus (short sword), Endurance, and Diehard are also good to add into the mix. While Jason can use weapons other than his signature machete, his style is also brutal power, hitting like a force of nature instead of a man. If you have space for a fill-in feat that fits the theme, you may want to take Godless Healing (The Inner Sea World Guide 287) as a way to explain Jason's undying nature.
A final consideration when it comes to Jason's feats, though, is the story feat Innocent Blood (Ultimate Campaign). You need to slay at least 50 intelligent non-combatants (handily taken care of in the character's backstory), and the benefits are a terror to behold. Initially it grants a +2 on Intimidate checks (+4 if you have 10 ranks or more), but if you slay at least 200 more innocent noncombatants, and a powerful foe who wants to bring you to justice, then any shaken target takes double the penalties when attacking you, making saves against your abilities, or making skill checks that resolve against you.
Gear, Template, and Story
The build thus far has reflected Jason as a living, breathing slasher. He was a holy terror, a mass murderer, and a force to be reckoned with. Despite all that, though, he was eventually killed. That was, until, he was literally struck by lightning, and brought back from the grave as an undead, undying brute. Simply adding the undead template isn't enough to bring across the undying nature of Voorhees, though. Ideally you would apply the lich template (potentially with his mask as the phylactery), but that requires the character to be a spellcaster. The Graveknight template is also applicable, though many of its abilities don't thematically mesh with Voorhees as a character. It does, though, give you the ability to rejuvenate even when you should be long dead.
Though Jason doesn't have gear in the traditional sense, he is known for the machete he carries. The same one that took his mother's head, according to most canon lore. The Murderer's Machete (Horror Adventures 215) is a direct homage to this blade. A short sword capable of dealing slashing damage as well as piercing, it provides a +2 bonus on Stealth and Survival when tracking, and once per day it lets you use cruel jaunt to teleport to a target suffering from a fear effect. The standard version is a +1 keen short sword, but the greater version is a +2 keen wounding short sword.
Lastly, you need to ask how much of your character is an homage, and how much a direct translation from the film. Did your version of Jason witness his mother's murder? Does he prey on teenagers, or on anyone who comes to his woods? Is he a local legend, or do people have no idea who he is? Is he thought of as a hero by the populace, killing bandits who hide out in his territory, or is he a terror that mothers warn their children with at night? Most importantly, is he a part of your party, or is he an antagonist that your players have to contend with?