Streamlined Spell Casting

Howdy, folks, and welcome to the first GURPSDay (and Game Geekery post) of 2017!

Fully 2/3 of the voters in last week’s end-of-year poll voted for more “Streamlining GURPS” posts as their #1 choice, so that seemed a good place to start off the new year. (The poll remains open, by the way — you can still make your voice heard!)

So this week, I offer up a very simple, very freeform magic system that I’ve used for a number of games with great success. Originally, I cobbled it together to represent Presto’s chaotic and unreliable — but extremely powerful — magic hat from the old D&D cartoon, but it comes in handy for a lot of one-shot games to get the spell casters up and running quickly.

Basically, the caster describes what it is she wants to accomplish, and the results of the dice roll (4d6) indicate how close to that goal she comes. There are no set spell lists, and each spell costs a fixed number of Fatigue Points.

I usually set the FP cost at 2 per casting, which means an average mage (HT 10-13) can cast 5 or 6 spells a day without resting or falling unconscious, but naturally this can be adjusted to allow for more or fewer castings. For direct damage effects, the simplest way is to assume 1d of damage per 1 FP spent to a maximum of 4 (or more, for very powerful casters). Targets still usually get an active defense of some kind (Dodge an incoming lightning bolt, DX roll to avoid tripping on marbles, etc.)

There is no relevant skill for spell casting. I give mages a Thaumatology skill, but that is for general knowledge of magic and so forth — the actual casting is accomplished with a static table (below), so skill levels are unnecessary.

To cast a spell, the mage first describes what she wants to happen. “I summon a crossbow to replace Bjorn’s broken one,” “I conjure up a rope bridge across the chasm,” “I look into the water of the pond and try to see where Olaf is being held,” that sort of thing. If it’s too powerful or game-breaking (“I conjure $75 billion worth of gold,” “I make the villain’s heart explode from two kingdoms away”), the GM can briefly talk it out with the player to come up with a compromise within the scope of what a mage can accomplish in the setting.

Once the goal is settled, the caster spends the appropriate FP cost and rolls 4d6: the usual 3d6 of one color/size (the Effect Results dice), plus 1d6 of a different color/size (the Effect Type die), and the GM compares those rolls to the below tables to figure out what happened.

Effect Results (3d6)

Roll Results
3-4 Effect works as intended or possibly better. Player chooses Type (ignore the Type die roll).
5-6 Effect works as intended. Effect Type die indicates Type (for all results unless otherwise noted).
7-8 Effect is close to what was intended.
9-11 Effect mostly works as intended but with small differences.
12-13 Effect mostly works as intended but with major differences.
14-15 Effect barely works as intended and with minor negative consequences.
16-17 Effect does not work as intended but instead creates negative effects.
18 Spectacular catastrophe and/or the opposite of intended effect occurs. GM chooses Type (ignore the Type die roll).

Note that the caster’s intended effect only outright fails on a roll of 16 or higher — as written, the system is biased towards success with increasing degrees of unwanted effects, but the GM can tweak the levels for different results.

Effect Type (1d6)

Roll Results
1 Player's Choice of Effect Type (Magic Item/Effect; Animal; Mundane Item; Food).
2 Magic Effect/Item (Flying Carpet; Teleportation Spell; Transformation Spell; Clone of Nearby Being; Whirlwind; Shrinking; Growing; Howling Wind; Snow Storm; Torrent of Water; Energy Beam; Energy Restraints; Sucking Wind; Levitation).
3 Animal (Hawk; Cow; Chicken; Pseudo-Dragon; Giant Flies; Giant Bat; Goldfish [in bowl]; Giant Rabbit; Termite Colony).
4 Mundane Item (Normal Carpet; Ropes; Glowing Marbles; Bucket; Shield; Horn; Notepad and Pen; Stop Sign; Cloud of Smoke; Frock and Wig; Hawaiian Shirt and Shorts; Frisbee; Weed Killer Spray Can; Cannon; Flower Petals; Water Hose; Telephone; Aircraft Carrier; Gas Mask; Toy Tank; Mousetraps; Bird Cage; Electric Fan; Mirror; Parachute; Blanket; Hot Air Balloon; Grooming Kit; Road Map; Flares; Radio; Travel Guide; Vacuum Cleaner; Dynamite; Bottle Caps).
5 Food (Birthday Cake; Carrots; Ham; Picnic Basket; Whipped Cream Can; Apple; Bananas).
6 GM's Choice of Effect Type.

The Animal and Food Effect Types are holdovers from the D&D cartoon; for some reason, it was very common for Presto to conjure both when using magic. They could easily be swapped out for some other type: Clothing, Weapons and/or Armor, Elements, Weather, etc.

Example One

Tawillager the Mage and his party find themselves trapped at the bottom of a deep ravine with no clear path up. Rather than attempt to climb the 30′ wall, Tawillager’s player says, “I wave my hands in a ridiculously intricate pattern and attempt to create a series of wooden ladders to the top.” He spends 2 FP to power the spell and rolls 4d6, which could go a number of ways.

Effect Results: 7 (Effect is close to what was intended.)
Effect Type: 2 (Magic Effect/Item.)

GM: “Magic energy snakes from Tawillager’s hands and forms into enough rope ladders to the top for everyone to ascend at once.”

Effect Results: 12 (Effect mostly works as intended but with major differences.)
Effect Type: 5 (Food.)

GM: “In a flash of light, a massive mound of potatoes appears against the wall of the ravine. It only reaches halfway to the top, however. You will need to make a DX roll to climb to the top of the mound, and then a Climbing (or default) roll to climb the last 15′ to the top.”

Effect Results: 16 (Effect does not work as intended but instead creates negative effects.)
Effect Type: 4 (Mundane Item)

GM: “Freezing winds shoot forth from your hands and cover the walls of the entire ravine in a slick sheet of ice. Any Climbing rolls without pitons or something similar will be at -6; those with will still be at -2.”


Example Two

Big Kay the Mage and her buddies are attacked outside a club by a cybernetically enhanced street gang. On her turn, Big Kay says “I give the gangers my kill face and throw a 4d fireball at the biggest one.” (Had the player wanted to cast an area of effect to damage all the gangers, I’d probably limit it to 2d instead.) She spends 4 FP (for 4d of desired damage) to power the spell and rolls 4d6, which could go a number of ways.

Effect Results: 5 (Effect works as intended. Effect Type die indicates Type.)
Effect Type: 3 (Animal.)

GM: “A huge dragon made of flames jets forth from your fingers and attempts to land on your target.” (The ganger can try to Dodge, as usual, but if he fails the damage is 4d burn.)

Effect Results: 14 (Effect barely works as intended and with minor negative consequences.)
Effect Type: 4 (Mundane Item.)

GM: “You summon a shiny chrome flamethrower that spews fire in an uncontrollable arc. It engulfs the target for a possible 3d damage (not 4d, due to the Results roll) but also catches you for a possible 1d damage.” (Both the ganger and Big Kay can try to Dodge.)

Effect Results: 18 (Spectacular catastrophe and/or the opposite of intended effect occurs.)
Effect Type: n/a (Doesn’t matter what it is; GM’s choice.)

GM: “Tendrils of eldritch flame shoot from your fingers, but rather than jetting towards the ganger they instead encircle and engulf you!” (Big Kay can try to Dodge, as usual, but if she fails the damage is 4d burn.)


This system is great for one-shots (where it doesn’t matter that the mage has no room to “grow”), and emulating wizards who are mighty and unpredictable, but there are a few things the GM should keep in mind:

  • Because a mage can at least propose anything she wants, it can be hard to differentiate characters if there are multiple casters in the party. They become a bit interchangeable.
  • For the same reason, the mages can easily overshadow other characters, though tweaking the FP cost per spell can alleviate that by restricting how frequently they can cast.
  • There is no (simple) way to differentiate a highly skilled mage from a novice. Without skill levels, the chance to produce a hugely damaging fireball is the same as that to light a torch on the wall.
  • And, most obviously, a system like this requires a lot of on-the-fly improvisation from both the caster and the GM, which can get draining (though for a four-hour convention game, it’s not really an issue).

Thoughts, suggestions, comments? If anyone else gives this a try sometime, I’d love to hear how it goes!

Happy New Year, everyone. Looking forward to big, big things for GURPS in 2017.


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  1. I’mma use this system for a disposable magic item in my campaign, to allow ANYone to try a wildcard attempt at crazy magic by breaking a runic stick or enchanted kitkat or something. This sounds fun!

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