Bestow Curse

Debuffing your foes is a perfectly respectable tactic in combat. Making an enemy easier to defeat, or less able to defeat you, is a very obvious step towards the ultimate goal of defeating them without being defeated. However, debuffs generally have a finite duration or can be easily dispelled. Not so a particular subset of the debuff - curses.

Bestow curse is a level 3 Cleric spell (level 4 for sorcerers and wizards, meaning probably don't bother) that places a permanent curse on any touched creature that fails a Will save. It isn't mind-affecting, it isn't a negative energy effect, and it is not subject to dispel magic. A curse can only be removed by remove curse (no joke!), break enchantment, limited wish and up. It lists three possible forms for the curse to take:

• A -6 penalty to an ability score (bringing it to a minimum of 1.)
• A -4 penalty on all attack rolls, saves, ability checks, and skill checks.
• Each turn, the target has a 50% chance to act normally; otherwise, it takes no action.

These are all quite nice effects, honestly. Reducing a casting stat by six can wreak havoc on spells available as well as save DCs, and a -4 to everything is a great across-the-board hindrance that will come up even outside of combat. Note that concentrating on a spell and trying to break a grapple are both standard actions, meaning the affected won't be able to do so if they're rendered "unable to take an action" for a turn.

Nice as these effects are, though, perhaps the most interesting feature of bestow curse is the next line: "You may also invent your own curse, but it should be no more powerful than those described above."

Yessir, bestow curse is entirely open-ended in letting you ruin someone's day in whatever way you can come up with. Call it Level 3 Wish, so long as you're wishing to wreck a kid's birthday party. What to do with such an accommodating spell, especially one set on such a decent baseline power level? Here, I've come up with a list of suggestions for curses you can inflict upon the DM's self-insert NPC when he least expects it:

The Subject...
-Requires four times as much food and water.
-Has its surface thoughts audible to nearby intelligent creatures.
-Receives a phobia of your choice.
-Is unable to use extradimensional spaces.
-Cannot use potions, wands or scrolls.
-Has its carrying capacity reduced to one-quarter.
-Loses all forms of damage reduction.
-Gains the druid's inability to wear metal.
-Gains an inability to handle metal objects.
-Has its move speed reduced by half.
-Loses all weapon and armor proficiencies, other than simple weapons, natural weapons, and unarmed strikes. If the subject has feats for which the lost proficiencies are prerequisites (such as Weapon Focus,) it loses the use of these as well.
-Takes a -8 penalty on all checks made using one skill, such as Climb or Spellcraft.
-Finds the enhancement bonus of any armor or weapons wielded by it become reversed and any special abilities are lost (For example, a +2 Flaming longsword would function as a -2 longsword.)
-Loses the ability to heal naturally (although he does not lose innate healing abilities such as fast healing or regeneration.) In addition, spells of the conjuration (healing) subschool only heal the target for half as much as normal.
-Must attempt to deal nonlethal damage whenever possible, taking a penalty of -4 on attack rolls with most weapons to do so.
-Requires 12 hours of sleep every night to be rested, rather than 8.
-Has all critical threats made against it automatically confirm, without requiring the attacker to reroll.
-Cannot cast defensively.
-Cannot charge or run.
-Is unable to take attacks of opportunity.
-Makes all rolls twice and keeps the worse of the two.
-Is rendered sterile (No, in combat this won't do anything [Please don't play the kind of game where it does] but it has excellent story potential in a 'nobility & intrigue' sort of setting.)

Note that page 28 of the Book of Vile Darkness also lists suggestions for possible curses, some of which are quite inspired, others of which seem imbalanced or unusual ("Subject cannot cast spells"? You really think that's okay?) Two of the more intriguing options include "Subject is struck deaf and blind," and "Every time the subject makes a d20 roll, a natural roll of 20 counts as a 1."

Bestow Greater Curse

As is often the case with overpaid game designers who don't feel like coming up with an entirely new idea, there is a variant of bestow curse that is higher level and has the word "Greater" slapped in front of it. The guideline for stakes on curses with the "Greater" prefix are upped as followed:

• One ability score is reduced to 1, or two ability scores take -6 penalties (to a minimum of 1.)
• A -8 penalty on all attack rolls, saving throws, ability checks, and skill checks.
• Each turn, the subject has a 25% chance to act normally; otherwise, it takes no action.

Naturally, of course, it also has the clause that you can make your own curse using simple household chemicals, so long as it's about as strong as the examples given. The higher power level of greater curses is tempting, but I'd be cautious not to overdo it, and most of the time would likely just settle for one of the three listed examples. Still, "you get to act one round in every four" is a pretty high power level, and I've come up with a few ideas.

The Subject...

-Cannot use any Charisma-, Dexterity-, or Intelligence-based skills, the Concentration skill, nor can it activate magic items that require a command word, a spell trigger (such as a wand), or spell completion (such as a scroll) to function.
-Automatically fails Reflex saves.
-Takes damage equal to the amount of damage it deals to others with natural or manufactured weapons. This does not extend to spells or other sorts of abilities.
-Has its land speed reduced to 5 feet.
-Cannot be healed by magical healing.
-Loses the use of all feats it possesses, just as if it suddenly failed to meet their prerequisites.
-Loses its Spell Resistance and all forms of Damage Reduction.
-Is harmful to its loved ones. Any creature within 100 feet that the subject is friendly to is automatically sickened until it gets more than 100 feet away. Any creature within 30 feet that the subject is friendly to is nauseated. Any creature that the subject is friendly to and physically touches takes 1d6 points of damage and 1 point of Charisma damage.

That last one is something of a literary classic, but you just know some smarmy DM is going to immediately thereafter have the subject declare his undying love for one of the PCs.