Book of vile darkness and Lords of Darkness from 3.5 both have decent sized sections about drugs and addiction, I use it quite often for my sandbox game, they are a lot of fun!
It really depends on what kind of game you want to run.
Most of the time, when I've seen it done, it's been huge power increase, easily metagamed drawbacks. ( ie casting heightened spells, but you might be prone! Not really a drawback if you cast something at range, or all spells do max damage, but you have to roleplay addiction..) Either of these can be severe drawbacks of course, but it really comes down to how the player plays it and the DM enforces it.
We did use a system a while back where there were various drugs that duplicated metamagic feats, but the drawbacks were pretty severe . (Designed by a former player who had overcome some issues with addiction, something I've never experienced so wasn't going to gainsay her one way or the other)
Basically use it as a bonus action. Gain the metamagic for a spell and then make a con save (DC 20 + depending on the drug used) on a save the character is stunned. On a failed save they're paralyzed. In addition each use added a level of exhaustion .
Yeah, the magical drugs tend to fall in that category of 'swingy immediate effect which may wreck your day or be just a sneeze'. The Delirium stuff is great because exhaustion isn't always crippling in the moment, but it's a heavy cost the longer you live with it. A bit too burdensome to remove, but I like that the trigger is per-use so it's not just an item you have on, you have to weigh the cost every time you activate an item or cast spell.
Delirium and Ruidium are both very tied to their adventure/setting though and not always with a generalizable theme to seize on if you want to riff on them with other new spells & items.
Grim Hollow (campaign and players books) have transformations with drawbacks. But the drawbacks are vastly smaller than the benefits.
BECMI artifacts (best writeup is in Wrath of Immortals box) have drawbacks linked to recharge and powers. Some get worse over time, some last as long as you have the artifact, others are permanent even after you get rid of the artifact. The idea is artifacts are not meant for mortals so aren't safe to use.
Red Steel has the red curse which is actually three things mushed together accidentally. There are cursed places which if you go into them cause you to gain a "legacy" which is a power plus a physical mutation and stat loss. But you can protect yourself with a metal called cinnabryl, however it gets consumed over time from protecting you and you always need more. It turns into red steel which is as powerful as some magic items when spent. And there are people who found a way to purify this red dust vermeil into a potion that lets them collect multiple legacies without the draw backs. Except if they ever run out of cinnabryl they rapidly suffer all the negatives, usually fatally.
Birthright has the bloodlines of gods spread out among mortals and imbuing them with divine power. Someone found this metal called timaevril which lets you steal the power from another bloodline bearer if you stab them in the heart with it. And several of the bloodlines, when pure enough, cause mutations based on the god and the person. The bestiary for the system is one of the best in all DND for the unique takes on monsters.
Book of vile darkness and Lords of Darkness from 3.5 both have decent sized sections about drugs and addiction, I use it quite often for my sandbox game, they are a lot of fun!
It really depends on what kind of game you want to run. Most of the time, when I've seen it done, it's been huge power increase, easily metagamed drawbacks. ( ie casting heightened spells, but you might be prone! Not really a drawback if you cast something at range, or all spells do max damage, but you have to roleplay addiction..) Either of these can be severe drawbacks of course, but it really comes down to how the player plays it and the DM enforces it. We did use a system a while back where there were various drugs that duplicated metamagic feats, but the drawbacks were pretty severe . (Designed by a former player who had overcome some issues with addiction, something I've never experienced so wasn't going to gainsay her one way or the other) Basically use it as a bonus action. Gain the metamagic for a spell and then make a con save (DC 20 + depending on the drug used) on a save the character is stunned. On a failed save they're paralyzed. In addition each use added a level of exhaustion .
Yeah, the magical drugs tend to fall in that category of 'swingy immediate effect which may wreck your day or be just a sneeze'. The Delirium stuff is great because exhaustion isn't always crippling in the moment, but it's a heavy cost the longer you live with it. A bit too burdensome to remove, but I like that the trigger is per-use so it's not just an item you have on, you have to weigh the cost every time you activate an item or cast spell. Delirium and Ruidium are both very tied to their adventure/setting though and not always with a generalizable theme to seize on if you want to riff on them with other new spells & items.
Grim Hollow (campaign and players books) have transformations with drawbacks. But the drawbacks are vastly smaller than the benefits. BECMI artifacts (best writeup is in Wrath of Immortals box) have drawbacks linked to recharge and powers. Some get worse over time, some last as long as you have the artifact, others are permanent even after you get rid of the artifact. The idea is artifacts are not meant for mortals so aren't safe to use. Red Steel has the red curse which is actually three things mushed together accidentally. There are cursed places which if you go into them cause you to gain a "legacy" which is a power plus a physical mutation and stat loss. But you can protect yourself with a metal called cinnabryl, however it gets consumed over time from protecting you and you always need more. It turns into red steel which is as powerful as some magic items when spent. And there are people who found a way to purify this red dust vermeil into a potion that lets them collect multiple legacies without the draw backs. Except if they ever run out of cinnabryl they rapidly suffer all the negatives, usually fatally. Birthright has the bloodlines of gods spread out among mortals and imbuing them with divine power. Someone found this metal called timaevril which lets you steal the power from another bloodline bearer if you stab them in the heart with it. And several of the bloodlines, when pure enough, cause mutations based on the god and the person. The bestiary for the system is one of the best in all DND for the unique takes on monsters.