Alternative psychedelic magic system: The ability to perceive and manipulate the world through paranormal means is gained through the use of a psychotropic drug. The MU class consists of those with the talent and training to channel the powers of the entheogenic elixir. Magic-users do not need a spell compendium and do not memorize spells, instead the MU takes a hit of the drug at the beginning of the day and thereby gains access to the number of spells corresponding to his or her level. The exact spells gained are determined randomly each time the drug is used. Each spell can only be used once during the 24 h period that the trip lasts. If a character that is not of the MU class ingests the drug they will suffer sever confusion and sickness, hallucinations, paranoia and risk permanent madness (25%).
Edit: Harley Stroh commented on this post on G+ and contributed some really neat ideas:
When I read the blog post title, I thought it meant that the act of casting magic / warping reality was addictive / addicting, which is also a pretty fun thought.
What could be the form of magic addiction? After a while casting 1st level spells doesn’t fullfil the need any longer? So you’re drawn to ever more potent spells … pushing the envelope of reality more and more.
It’s almost as if each casting should require a saving throw / Fort check. Failed = black out from the high. Nat 1 = OD.
And what does magic withdrawal look like?
Hm, I guess a MU might get a cumulative negative modifier to all die rolls for each day that passes without using their drug.
This idea started out as an idle thought when I was trying to sleep, but I think I’ll use it in my upcoming Vornheim game.