So instead, I bring you a home brew which I originally created for D&D 3.5. At the time I had a character who needed to have a lot of vices. I wasn't satisfied with any of the drugs I found in the Book of Vile Darkness, because they all lacked a visceral element to them. I envisioned this character injecting themselves with heroin in a fantasy world where nobody had ever heard of a syringe.
And thus, the Corpse Mote was born. There is no upside to using Corpse Motes, as there is with many drugs available in the game. This is purely a detriment to whatever character uses it, and is primarily intended for those who take their role playing seriously. As such, it may not work in most games.
Corpse Motes are created when maggots feasting on a corpse are caught up in the negative energy used to turn that corpse into an undead.
Corpse Motes are larger than normal maggots, and grow spines along one side of their body not unlike those of a porcupine. Three powerful pincers, which are used to grapple mice and other prey, surround tooth-filled prehensile tube which serves as their mouth.
Once a corpse mote's prey has is firmly held by the pincers, it latches on to the victim with its mouth. It then injects a powerful paralytic into the victim with its teeth, which allows the creature all the time it needs to suck its prey's innards out for sustenance. For a Corpse Mote's intended prey, this paralytic is a cruel death sentence. For a small or medium sized character, however, the paralytic causes a powerful and addictive euphoria.
Many Necromancers, whether by through intentional experimentation or simply by chance, become addicted to the venom of the Corpse Mote. Injection of the drug is handled by allowing a Corpse Mote to bite you, then squeezing it to death. In its death throes, the vermin will empty its venom sacks into the user's bloodstream.
This can be an extremely painful procedure, since there's no easy way to avoid being injured by the spines of the Corpse Mote while squeezing it to death. The sharp pincers used to grapple prey usually cause multiple painful lacerations before the injection is complete as well. However, many choose to make the pain part of the experience, rather than attempt to mitigate it. Others keep metal gauntlets, minions, or plucked-and-depincered corpse motes around to handle injections relatively painlessly.
GAME RULE INFORMATION
Every time a character is bitten by a corpse mote, they get a will save (DC:5) to resist addiction. With each subsequent bite within 1 year of the last bite, the DC rises by 5.
An addicted character takes a -1 penalty to Wisdom to account for impairment caused either by euphoria, or by jonesing for another fix. This is a constant affect until the character has recovered from their addiction.
An addicted character must be bitten by a corpse mote once every 24 hours or they take one negative level, and begin to suffer withdrawals.
Withdrawals begin 24 hours after an addicted character's last dose, and end either when the character has beaten their addiction, or when they give in to addiction and 'shoot up' with another Corpse Mote.
Every 48 hours after the beginning of withdrawals, an addicted character receives a will save (DC: 5 times the character's effective level.) If the will save succeeds, the character has overcome their addiction. If the save fails, the character receives one negative level. Characters must have the desire to quit in order to receive a will save.
48 hours after a character reaches an effective level of 1, they automatically overcome their addiction, whether or not they have a desire to do so.
A character who overcomes their addiction to Corpse Motes must still go through recovery.
Once a character has overcome their addiction, they must must rest. For every 24 hours of rest after overcoming their addiction, they regain 1 of their lost levels. The rest does not need to be consecutive. This continues until the character is fully recovered. Note that rest does not necessarily mean sleep, but the character must be relaxed and restful during this period.
If, at any time during the next year, the character is bitten by a Corpse Mote, they are instantly re-addicted to the substance, and must go through withdrawals and recovery again in order to overcome their relapse. After a year, if the character is bitten by a corpse mote, they are allowed a will save to resist addiction, but the will save is 20 to start with, rather than 5. As per usual, the DC raises by 5 each time the character is bitten within 1 year of the previous bite.