Special Damage

Getting hit by weapons or monsters isn't the only way a character can get hurt. Indeed, the world is full of dangers for poor, hapless player characters, dangers the DM can occasionally spring on them with glee. Some of the nastier forms of damage are described below.

Falling

Player characters have a marvelous tendency to fall off things, generally from great heights and almost always onto hard surfaces. While the falling is harmless, the abrupt stop at the end tends to cause damage.
When a character falls, he suffers 1d6 points of damage for every 10 feet fallen, to a maximum of 20d6 (which for game purposes can be considered terminal velocity). This method is simple and it provides all the realism necessary in the game. It is not a scientific calculation of the rate of acceleration, exact terminal velocity mass, impact energy, etc., of the falling body.
The fact of the matter is that physical laws may describe the exact motion of a body as it falls through space, but relatively little is known about the effects of impact. The distance fallen is not the only determining factor in how badly a person is hurt. Other factors may include elasticity of the falling body and the ground, angle of impact, shock wave through the falling body, dumb luck, and more.
People have actually fallen from great heights and survived, albeit very rarely. The current record-holder, Vesna Vulovic, survived a fall from a height of 33,330 feet in 1972, although she was severely injured. Flight-Sergeant Nicholas S. Alkemade actually fell 18.000 feet—almost 3.5 miles— without a parachute and landed uninjured!
The point of all this is roll the dice, as described above, and don't worry too much about science.

Paralysis

A character or creature affected by paralysis becomes totally immobile for the duration of the spell's effect. The victim can breathe, think, see, and hear, but he is unable to speak or move in any manner. Coherent thought needed to trigger magical items or innate powers is still possible.
Paralysis affects only the general motor functions of the body and is not the ultimate destroyer of powerful creatures. It can be particularly potent on flying creatures, however.
An example of paralysis: The adventurers encounter a beholder, a fearsome creature with magical powers that emanate from its many eyes.
After several rounds of combat, the party's priest casts a hold monster spell, paralyzing the creature. The paralyzed beholder can still use the spell-like powers of its eyes and can still move about (since it levitates at will). But, on the other hand, it is not able to move its eyestalks to aim. Since all of its eyes were most likely facing forward at the moment of paralysis, the adventurers cleverly spread out in a ring around the creature. To attack one or two of them with its powers, the beholder must turn its back on the rest.

Energy Drain

This is a feature of powerful undead (and other particularly nasty monsters). The energy drain is a particularly horrible power, since it causes the loss of one or more experience levels!
When a character is hit by an energy-draining creature, he suffers normal damage from the attack. In addition, the character loses one or more levels (and thus Hit Dice and hit points). For each level lost, roll the Hit Dice appropriate to the character's class and subtract that number of hit points from the character's total (subtract the Constitution bonus also, if applicable). If the level(s) lost was one in which the character received a set number of hit points rather than a die roll, subtract the appropriate number of hit points. The adjusted hit point total is now the character's maximum (i.e., hit points lost by energy drain are not taken as damage but are lost permanently). The character's experience points drop to halfway between the minimum needed for his new (post-drain) level and the minimum needed for the next level above his new level.
Multi-class and dual-class characters lose their highest level first. If both levels are equal, the one requiring the greater number of experience points is lost first. All powers and abilities gained by the player character by virtue of his former level are immediately lost, including spells. The character must instantly forget any spells that are in excess of those allowed for his new level. In addition, a wizard loses all understanding of spells in his spell books that are of higher level than he can now cast.
Upon regaining his previous level, the spellcaster must make new rolls to see if he can relearn a spell, regardless of whether he knew it before.
If a character is drained to 0th level but still retains hit points (i.e., he is still alive), that character's adventuring career is over. He cannot regain levels and has lost all benefits of a character class. The adventurer has become an ordinary person. A Restoration or Wish spell can be used to allow the character to resume his adventuring career. If a 0th-level character suffers another energy drain, he is slain instantly, regardless of the number of hit points he has remaining. If the character is drained to less than 0 levels (thereby slain by the undead), he returns as an undead of the same type as his slayer in 2d4 days. The newly risen undead has the same character class abilities it had in normal life, but with only half the experience it had at the beginning of its encounter with the undead who slew it.
The new undead is automatically an NPC! His goals and ambitions are utterly opposed to those he held before. He possesses great hatred and contempt for his former colleagues, weaklings who failed him in his time of need. Indeed, one of his main ambitions may be to destroy his former companions or cause them as much grief as possible.
Furthermore, the newly undead NPC is under the total control of the undead who slew it. If this master is slain, its undead minions gain one level for each level they drain from victims until they reach the maximum Hit Dice for their kind. Upon reaching full Hit Dice, these undead are able to acquire their own minions (by slaying characters).
Appropriate actions on the part of the other player characters can prevent a drained comrade from becoming undead.

Poison

This is an all-too frequent hazard faced by player characters. Bites, stings, deadly potions, drugged wines, and bad food all await characters at the hands of malevolent wizards, evil assassins, hideous monsters, and incompetent innkeepers. Spiders, snakes, centipedes, scorpions, wyverns, and certain giant frogs all have poisons deadly to characters. Wise PCs quickly learn to respect and fear such creatures.
The strength of different poisons varies wildly and is frequently overestimated. The bite of the greatly feared black widow spider kills a victim in the United States only once every other year. Only about 2% of all rattlesnake bites prove fatal.
At the other extreme, there are natural poisons of intense lethality. Fortunately, such poisons tend to be exotic and rare — the golden arrow-poison frog, the western taipan snake, and the stonefish all produce highly deadly poisons. Furthermore, the effect of a poison depends on how it is delivered. Most frequently, it must be injected into the bloodstream by bite or sting. Other poisons are only effective if swallowed; assassins favor these for doctoring food. By far the most deadly variety, however, is contact poison, which need only touch the skin to be effective.
Paralytic poisons leave the character unable to move for 2d6 hours. His body is limp, making it difficult for others to move him. The character suffers no other ill effects from the poison, but his condition can lead to quite a few problems for his companions.
Debilitating poisons weaken the character for 1d3 days. All of the character's ability scores are reduced by half during this time. All appropriate adjustments to attack rolls, damage, Armor Class. etc., from the lowered ability scores are applied during the course of the illness. Furthermore, the character moves at one-half his normal movement rate.
Finally, the character cannot heal by normal or magical means until the poison is neutralized or the duration of the debilitation is elapsed.

Treating Poison Victims

Fortunately, there are many ways a character can be treated for poison. Several spells exist that either slow the onset time, enabling the character the chance to get further treatment, or negate the poison entirely. However, cure spells (including Heal) do not negate the progress of a poison, and Neutralize Poison doesn't recover hit points already lost to the effects of poison. In addition. characters with herbalism proficiency can take steps to reduce the danger poison presents to player characters.