Shadowrun Magic for Stars Without Number and Other OSR Games

Shadowrun is a terrible system with an awesome concept behind it, which is why at least once a month someone on r/rpg asks what the best non-Shadowrun system is for playing Shadowrun.  The most common answer– and the correct one in my opinion– is Stars Without Number. 

Now SWN has psionics rules, and the deluxe version also has some "space magic" rules, but neither quite work like Shadowrun magic does.  To summarize:

In Shadowrun, spells are level-less, so any mage can potentially cast any spell (supplements add some special exceptions because it's Shadowrun, of course they do).  When casting a spell you pick the force– the power you'l cast it at– resolve the effects, and then roll for "drain", which means you might take either stun or physical damage from your own spell.  The higher the force, the stronger the spell and the more drain you'll take.

It's not Vancian at all, and nothing I've seen in the OSR quite works that way.  Here's a Shadowrun magic hack that comes really close. 

Pick an OSR game of your choice to play "Shadowrun" with.  As mentioned, SWN is probably the best choice, but Esoteric Enterprises would work too, as would a few others.  It needs to be a game with a magic system though. 

Spells can be leveled as in most systems or level-less; this works either way.  You learn spells as normal; this just changes how you cast them. 

Step One

Pick a spell to cast.  Unlike in normal OSR systems, you can cast spells up to twice the spell level you'd normally be able to cast, so like a first-level wizard could cast level 2 spells, etc.  If using level-less spells, imagine you learn a new spell level every other character level like in most systems. 

There will of course be a cost to casting spells above your normal casting level.  You'll see...

Step Two

Resolve the spell's immediate effects as normal.  Drain comes after the spell is cast.

Step 3

Now comes the price: drain, in the form of temporary wisdom or constitution damage. 

Make a save versus magic, or a wisdom save, or in Stars Without Number, a mental save.

Now take drain.  In the five spell level system of Stars Without Number, this is d4 for a level 1 spell, d6 for a level 2 spell, and d8, 10, d12, so on.  In the nine spell level system used by most games, drain is 1/d2/d3/d4/d5/d6/d8/d10/d12. 

If the spell was a level you'd normally be able to cast– so its level was no higher than half your character level rounded up– drain causes temporary wisdom damage.  If higher, it causes constitution damage.  If you passed the save, the drain is halved, rounded down. 

Temporary WIS and CON damage lowers your modifiers as normal, potentially reducing your hit points, perception, saves vs magic, or whatever those ability scores do in your system. 

If CON goes to zero, you're dead.  If WIS goes to zero, you're just knocked unconscious. 

So as you go up in level, you can a) cast higher-level spells, b) cast higher-level spells safely, and c) pas the save more often, thus taking less drain. 

The number of spells you can cast per day (or per week since the ability damage does take time to heal) still doesn't scale as well as spellcasting ability does in most OSR games.  This works best if you can increase WIS, and maybe also CON, as you level up.  If your game of choice doesn't allow that, maybe make it so drain is completely avoided if you either pass the save by ten or more, or roll a nat 1 or 20 (whichever is good obviously) on it.