GLOG Spellcasting Feat

Discover a feat for 5th Edition that lets wizards and other spellcasters use GLOG spellcasting.

Chapter VIII: The Gamble, Or, A Small Miscalculation

The wizard, Gleana the Grey stood quietly near the perimeter of a small clearing. A wyvern stalked menacingly along the far edge. Lashing its serpentine tail, it gave a low growl.

Then, almost imperceptibly, it’s muscles tensed as it prepared to attack.

Calmly, Gleana fished a small brownish lump from a pouch at her waist. As she squished the lump between her fingers, a pungent aroma wafted up — the unmistakable smell of sulphur, tinged with the subtler stink of bat guano. Pointing her stained fingers at the snarling wyvern , Gleana intoned a quick jumble of syllables.

For a moment, nothing happened… Then, a reddish light lanced toward the reptilian monster. As the beast began to leap forward, the air around it erupted with fire.

Smiling grimly, Gleana balled up her fist and pantomimed casting a pair of dice. The flames appeared to burn even brighter. The wyvern’s growl turned to a shriek as it was consumed by the blossoming flames.

But something was wrong! An unexpected spur of magic had bloomed. Scalding energy washed back over Gleana. Her body seemed to fold in on itself; organs shrinking, muscles contracting, bones snapping under an immense pressure before rapidly re-calcifying.

When the pain finally receded, her wizard’s robes hung loose around her shoulders. Taking a step forward, she nearly stumbled when her foot slipped right out of her low boot. Looking up, it seemed to her that the world had expanded somehow.

No, she realized, she had shrunk!

Suddenly, a second wyvern charged into the clearing.

Gleana fumbled for her component pouch. But the pouch, and its oversized belt, had fallen to the ground! With a wordless yelp, she turned and scrambled back into the relative safety of the forest as fast as her tiny feet would carry her!

What Is The GLOG?

The creator of the Goblin Laws of Gaming (GLOG), Arnold Kemp of Goblin Punch fame, called the GLOG as a set of fantasy heartbreaker1 RPG rules. I suppose, it could also be described it as a branchlet of the OSR.2 However you represent it, the GLOG’s adherents seem to have a particular penchant for creating new character classes especially spellcasting classes.

I won’t name myself a member of those lofty ranks. But, I will take a stab at a little GLOG inspired feat for 5E.

Casting Dice

Arguably, the most distinctive feature of GLOG spellcasting is the casting die3. Each casting die is a d6 and, essentially, acts as a spell slot. However, you can use multiple casting dice in a single casting to make a spell more powerful. Basically, by using two or more casting dice you are upcasting4 the spell.

So, why not just use spell slots or something like the DMG’s spell points5 variant?

Because, casting dice have two additional features:

  1. About half of the die you roll are immediately returned to your casting pool. Thus, casting dice let you cast a random number of additional spells.
  1. If you roll doubles or (worse) triples on your casting dice, something (very) bad happens. Therefore, using more casting dice makes a spell more powerful but also makes casting it more interesting dangerous!

Adapting The GLOG For 5th Edition

I’d like to adapt the Arnold’s casting dice into 5E’s brand of spellcasting. I’d like to keep as much of their flavour as possible. But, I don’t want to go so far as creating an entire parallel spellcasting regime. Also, I’d like every caster to have access to the casting dice. How best to do all that?

Fifth Edition characters can be thought of as having six components: Race, Class(es), Subclass(es), Background, Items and Feat(s). Really, I could introduce GLOG spellcasting using any of these components. However, I’m going to build a feat since it lets me offer GLOG spellcasting to every type of spell caster.6

  1. My GLOG feat will give a player a pair of casting dice. However, rather than using these dice to cast spells directly, players will use them to upcast their spells. This is a clear divergence from GLOG spellcasting, but should help prevent this feat from feeling overpowered.

Thus, these two casting dice don’t let wizards et al. cast more spells, they let them cast more powerful spells. So, I think I’ll call them upcasting dice for clarity’s sake.

  1. In keeping with GLOG tradition, the dice will be available for reuse about half the time. When a player rolls a 4, 5 or 6 they can use that die again. Otherwise they have to wait until their character finishes long rest.
  1. Players can choose to use two dice at a time but rolling doubles is bad…

If a player rolls doubles the spell still works, but they must roll on a random table to find our what unfortunate thing happens to their character. I’m calling this the Magical Mishaps table and one of the options will lead to a second Magical Mutations table.

In keeping with 5E’s design ethos, both mishaps and mutations are relatively mild and completely temporary.

  1. Since, I’m only allowing two upcasting dice, rolling triples is off the table.

So, without further ado here is my GLOG spellcasting feat.

Feat: GLOG Spellcasting

Prerequisite: Spellcasting Slots

You’ve learned how to exert your will on your spells in order to increase their power. You gain two upcasting dice for your upcasting dice pool. Each upcasting die is a d6. You can spend one or both upcasting dice when you cast a spell using a spell slot. For each die spent, modify the spell according to the At Higher Levels section of the spell’s description.

  • Chose how many upcasting dice you want to invest in your spell, and remove them from your casting dice pool.
  • Cast your spell using a spell slot and roll the invested dice.
  • Dice that show a result of 4-6 are immediately returned to your upcasting pool. Otherwise, they are returned after a long rest.

If you spend two casting dice at once you risk a mishap.

  • If you roll doubles on your upcasting dice, you must immediately roll on the Magical Mishaps table.

Magical Mishaps

Roll a d6 to determine your mishap.

  1. You suffer one level of exhaustion.
  2. Your maximum hit points are reduced by 1d6. They return to normal after a long rest.
  3. You are blinded for 1d6 turns.
  4. You suffer a magical mutation for 1d6 turns, then make a DC 10 Constitution saving throw at the beginning of your next turn. On a failed save, the mutation lasts for 1d6 days. Determine your mutation by rolling on the Magical Mutations table.
  5. You cannot cast spells for 1d6 turns.
  6. You are frightened of all creatures for 1d6 turns.

Magical Mutations

Roll a d6 to determine your mutation.

  1. You grow a second head. That extra set of eyes and ears come in handy and you have advantage on perception checks. However, you have disadvantage on deception checks — your second head has a lousy poker face.
  2. You grow webbed feet and gills. You gain a swimming speed of 30 feet and you can breath under water. However, you must be submerged in water to benefit from a long rest.
  3. Your blood turns to acid. As a side effect, poison is rendered inert when it reaches your bloodstream. You are resistant to poison damage. Also, your blood vessels are immune to acid damage. Sadly, the rest of you is not. When you take slashing or piercing damage, you take an additional 1d6 acid damage.
  4. Your hair transforms into leaves and your skin toughens to tree bark. You have resistance to bludgeoning damage. Unfortunately, you also gain vulnerability to fire damage.
  5. Your body shrinks. If you are a medium creature you become small, if you are small you become a tiny creature. Your smaller size gives you advantage on Dexterity saving throws. However, you lose 5 feet of movement.
  6. Your body adapts to the dark. You grow antennae and your skin becomes translucent. You gain 15 feet of blindsight. Also, at the start of each minute that you are exposed to daylight, you take 1d6 radiant damage.

Example: Fireball

Casting Fireball with a 3rd level spell slot causes 8d6 worth of fire damage.7 However, according to the spell’s At Higher Levels section, casting Fireball “using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.”

Thus, if our hapless wizard, Gleana had used a single upcasting dice the spell’s damage increases to 9d6; she would have effectively casts the spell at 4th level. As it happens, Gleana gambled two upcasting dice; the spell did 10d6 fire damage but she also risked a magical mishap. And, as we’ve seen, magical mishaps are aptly named!

Additional Reading

  • Upcasting Feat PDF — A handy dandy PDF describing my GLOG upcasting feat.
  • The GLOG: Wizards — An introduction to GLOG spellcasters, by Arnold Kemp. (Don’t take my word for it, get it straight from the horses mouth!)


  1. A Dungeons & Dragons knock-off.
  2. The Old School Renaissance or Revival (OSR), is a romantic reimagining of 1970s Dungeon’s & Dragons style play.
  3. Casting dice are sometimes referred to as magic dice.
  4. Upcasting is, for example, casting a first level spell with a second level spell slot.
  5. Found on page 288 of the Dungeon Master’s Guide.
  6. A magic item would also work, but I’m sticking with a feat.
  7. Assuming a target fails its saving throw.

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