Nothing as of yet.
But.... off the top of my head...
You could have a disease track to reflect the effects of addiction to the drug, with each intake requiring an Endurance check to see if the character gets worse (but not better.)
Decide on a period of time between doses, then require an Endurance check after that period of time to see if the character's condition worsens or improves.
As for the drug itself, simply make it a potion with some encounter-long effect. Something useable, with no -immediate- downside. The downside comes later.
So....
Phial of Rakhasa's Whim
Lvl 6 150 gp
Lvl 16 3,600 gp
Lvl 26 90,000 gp
Alchemical Item
Power (Consumable): Minor Action. You get a +2 drug bonus to damage rolls until the end of the encounter. As well, every time you spend a healing surge, you heal 2 extra hit points. You are subject to an attack at the end of the encounter: +17 vs. Fortitude. If you are hit, you contract Whimsical Hunger, Level 8, or worsen if already under the effects.
Level 16: +4 to damage rolls, 4 extra hit points, +27 vs. Fortitude, Level 18 disease
Level 26: +6 to damage rolls, 6 extra hit points, +37 vs. Fortitude, Level 28 disease
Whimsical Hunger Level 8+ disease
Endurance: Improve DC 17+half disease level, maintain DC 11+half disease level, worsen 10+half disease level or lower.
Special: You cannot improve from this disease if you have taken a Phial of Rakhasa's Whim in the past week.
- The Target is Cured
- The Target heals 2 Points less when he spends a healing surge unless he is under the effects of Phial of Rakhasa's Whim
- Initial Effect - The target heals 2 points less when he spends a healing surge unless he is under the effects of Phial of Rakhasa's Whim and whenever he enters an encounter, he must roll Disease level+5 vs Will or be dazed until he consumes a Phial of Rakhasa's Whim.
- Final Effect - The target is dazed while not under the effects of Phial of Rakhasa's Whim, and gains 4 less hit points whenever he spends a healing surge.
