Slasher
Slashers are entities of Interlife Earth that seem to have no other purpose but to violently kill. They usually appear more or less human, but often have scarred or disfigured faces (and perhaps other body parts as well), which they frequently conceal behind masks and other coverings.
Origins
The first known slasher, Thomas Deacon, first made his appearance known in 1978 at Camp Bountiful, where he killed at least twelve people before finally being temporarily dispatched. Since then, not only has Deacon reappeared, but other slashers have arisen. The total number of slashers in existence is unknown, but there are reliable reports of at least two hundred and thirty-nine worldwide (some of whom, however, may be no longer active). Many other murder sprees may or may not have been the work of unknown slashers.
The evidence seems to suggest that slashers used to be human—not least because in many cases, including that of Thomas Deacon, their familial descent and their pre-slasher history are known. Some people believe that slashers are alien beings of pure evil, and in cases where they seem to have previous histories it's because the slashers have replaced their namesakes and taken their forms, but there's no evidence to support this. Others believe that those people were never human at all, but were always slashers whose nature simply didn't become obvious until years after their births. If slashers were once human, however, then what triggers their transformation is unclear. They may be some form of undead; they may be possessed by some malevolent entity from the Gap or elsewhere; they may have made some sort of bargain with an unknown force that has changed them to their current state. Regardless, the transformation seems to happen only to people who already have some tendencies toward the slasher mindset; those people who are known to have become slashers have been, without exception, antisocial at best and usually downright murderous even before they were recognizably slashers.
Behavior
Slashers have no society to speak of; their only goal seems to be to maim and kill as many people as possible. They cannot be reasoned with, and can rarely be intimidated. Most slashers go about their business in complete silence, never speaking a word, although a few delight in taunting their victims, and may toss off a nasty one-liner after a kill.
Some slashers have preferences as to the kinds of victims they slay, a predilection for teenagers being particularly common—though that won't necessarily stop them from killing others who get in their way. Others are more indiscriminate, being equally content to kill a person of any age, ethnicity, and social class. Many slashers also have favorite weapons they like to use in their kills, though, again, there are others who simply use whatever is most convenient, or even go out of their ways to find novel methods of dispatching their victims. Generally, however, slashers do prefer to kill in ways that lead to blood and mutilation; most slashers, given the choice, would, for instance, prefer to kill by stabbing than by suffocation. Slashers generally rely on their sheer durability and doggedness to get what they want, seldom formulating any plans more complicated than waiting in ambush. Some rare slashers, however, are smart enough to set traps and to use cleverer means of getting their victims. Even the dullest slashers enjoy taking victims by surprise, the better to deal a decisive blow, and may be willing to hide for hours in a closet or other enclosed space to leap out at a propitious moment. Still, they are also likely to stalk victims, often over long distances, their untiring nature (and their short-distance translocational ability) ensuring that no matter how far a victim tries to run, the slasher will catch them eventually.
On those very rare occasions when two slashers have met, they have either ignored each other completely and gone separately about their individual slaughters, or seen each other as rivals and immediately fought—though slashers seem no more to be easily dispatched permanently by other slashers than by ordinary people. The few reported cases of slashers working together for extended periods have not been verified, and may be no more than rumors.
Slashers generally have no interest in, nor power over, ghosts. However, they may still come into conflict with ghosts if, for example, a slasher threatens a mortal toward whom a ghost feels protective, or if a slasher's actions seem likely to result in the demolition of a haunt.
Powers
In addition to their sheer physical power, slashers have a number of abilities that seem supernatural in origin. Most slashers seem to have no trouble sensing their surroundings even in complete darkness, and their ability to get around in silence seems uncanny enough that it may have some supernatural component. More obviously, slashers are able to teleport short distances to get ahead of prey or position themselves in a good spot for an ambush, and can quickly clean up bloodstains or remove other evidence of their crimes. For whatever reason, however, these latter powers only seem to be usable when no one is looking; the slasher is incapable of using them when observed by any intelligent being.
Perhaps the slasher's most notorious power, however, is its simple resistance to—and recovery from—injury. Not only is it hard to damage in the first place, but its wounds heal with unnatural rapidity, though particularly severe wounds may still leave scars. Even a slasher that seems to have taken enough damage to kill it may rise moments later to continue its assault.
Weaknesses
Physically, slashers have few or no weaknesses. Their strength and fortitude surpass those of most humans, and their singlemindedness renders them difficult to dissuade from their purpose. On the average, however, they are not particularly intelligent, and it may be possible to outwit them.
Though it's very hard to keep a slasher down by injury, it isn't completely impossible. Oddly, for whatever reason, slashers seem somewhat more vulnerable in one-to-one fights than when facing multiple foes. In the latter case, they're even more resilient than usual, and virtually nothing can stop them for long, but in single combat certain means, such as beheadings, do seem to have at least a chance of putting an end to the slasher's activity for a while, and the same may be attained by "killing" the slasher enough times. Furthermore, most slashers do have some special weakness that can be exploited to defeat them. This weakness is different for each slasher, and may require considerable research (and/or trial and error) to find, but it may provide the best chance of stopping its depredations. However, even a slasher that is put down by some of those means still may return months or years later—even if its body has been completely destroyed and there seems no way it could possibly come back. If there is a reliable way to destroy a slasher for good, beyond any possibility of its return, no one seems yet to have found it.