Designing Spells for D&D

What a Spell Represents in D&D

In the Player’s Handbook, a spell is a discrete magical effect that a PC or creature can produce by spending resources: usually spell slots, sometimes uses of a feature or charges from a magic item. Spells come in levels (from 0 for cantrips up to 9th level) and belong to one of the schools of magic (Evocation, Illusion, Necromancy, and so on).

The description of a spell is always broken down into a few key lines:

• Name & school line – the spell’s unique name and its school, often with the classes that can cast it.
• Casting time – Magic action, Bonus Action, Reaction, or a longer casting time.
• Range – a distance, self, or touch; sometimes combined with an area of effect.
• Components – Verbal (V), Somatic (S), and/or Material (M) components.
• Duration – instantaneous, concentration, or a fixed time span.
• Effect text – what the spell actually does: damage, control, buffs, debuffs, utility, and so on.

When you create a new spell, you’re really deciding what each of these lines should say and how powerful the effect should be compared to existing spells of the same level.

DMG Guidelines for Creating New Spells

The Dungeon Master’s Guide recommends using existing published spells as models. When you design something new, keep these principles in mind:

• Unique name. Give the spell a distinctive name that players will remember. Avoid names that could be confused with official spells at your table.
• Balance. If a caster would want to use your spell every turn, it’s probably too strong for its level. Likewise, if nobody would ever prepare it, it may be too niche or too weak.
• Class identity. Make sure the spell fits the identity of the classes that can cast it. Healing and resurrection magic is usually divine; big blasting evocations feel arcane; subtle charms fit bards, warlocks, and enchanters.
• Duration, range, and area. Longer duration, higher range, or larger areas are all forms of power. A modest effect with a huge area can easily overshadow other options at the same level.
• Real utility. Avoid spells that only work in hyper-specific situations (“works only against oozes”, etc.). The more often a spell can come up in play, the more attractive it is.

The goal isn’t to create perfect mathematical balance, but to land in the same power band as the official spell list so players can swap your spell into their repertoire without overshadowing the rest of the game.

How Much Damage Should a Spell Do?

For spells that deal damage or restore Hit Points, the DMG offers a simple spell damage table. It suggests roughly how many dice a spell of a given level should roll for:

• A single target – higher damage per target.
• Multiple targets – lower damage per target since you can hit a group.

As a rule of thumb:

• Cantrips start around 1d10 to a single target or 1d6 in an area.
• Level 1–3 spells sit in the 2d10–5d10 / 2d6–6d6 range.
• High-level spells climb up toward 15d10 / 16d6 at 9th level.

The table assumes the spell deals half damage on a successful save (or on a miss, for attack rolls). If your spell deals no damage on a success, you can usually raise the damage by about a quarter and still stay reasonable.

You don’t have to use exactly the same dice. Swapping 1d10 for 2d4 keeps the average close while changing the feel of the roll. The important part is that the average damage matches the level and doesn’t dramatically outpace official spells like Fire Bolt, Guiding Bolt, or Fireball.

Start with the Spell’s Role and Concept

Before you worry about dice and wording, decide what the spell is supposed to do in play. The Arcanaria Spell Builder asks you to choose a broad role:

• Damage – blasting, weapon-like attacks, and elemental strikes.
• Control – restraining, pushing, slowing, silencing, or locking areas down.
• Support – buffs, debuffs, advantage / disadvantage, or protective magic.
• Utility – exploration, social tricks, movement, or information.
• Healing – restoring HP or cleansing conditions (using the damage table in reverse).

A good custom spell usually has one main job. If your idea combines massive damage, a strong debuff, and crowd control, try splitting that idea into two or three smaller spells instead.

The Anatomy of a Custom Spell

When you use the Arcanaria Spell Builder, you provide a short description of your concept plus a few mechanical choices. The builder then fills out all the standard entries of a spell:

• Name & school line. The AI proposes a unique name and school based on your concept and role.
• Level. You choose the spell level; the builder uses the DMG damage guidelines for that level.
• Casting time & range. You can bias toward quick, close-range spells or slower, long-range rituals.
• Target mode. Single target, small group, or area of effect, which influences how much damage is appropriate.
• Components & duration. The builder keeps to familiar patterns (instantaneous blasts, concentration for ongoing control, etc.).
• Rules text. The output is formatted like a Player’s Handbook spell: clear saving throws, attack rolls, and scaling rules.

You stay in control of the final result. If a spell looks too strong for your campaign, you can dial down the level, reduce the range or area, or remove a secondary rider effect.

Keeping Your Custom Spells Table-Friendly

Even with good guidelines, every table has its own tolerance for wild magic. Here are a few tips to keep homebrew spells fun rather than frustrating:

• Compare to official spells. Always sanity-check a new design against a few published spells of the same level and role.
• Avoid stacking too many riders. A spell that deals damage, imposes a strong condition, and grants ongoing advantage can feel unfair. Pick one or two key effects.
• Watch concentration. Concentration is a powerful limiter. If a spell feels very impactful over time, it probably should require concentration so it competes with other options.
• Test in play, then adjust. Don’t be afraid to tweak numbers after a session or two. You can raise or lower the level, change the save, or narrow the area if it’s stealing the spotlight.

Remember: DM approval is always required. Arcanaria helps you draft spells, but your group decides what becomes canon at the table.

How the Spell Builder Form Works

The Spell Builder is designed to mirror the way designers actually think about spells: first the idea, then the mechanics. Each field you fill in directly shapes the AI’s output.

Spell concept

This is the heart of your spell. In one to three sentences, describe what the spell should look like and accomplish. Mention elements such as:

• damage type (fire, necrotic, radiant…)
• movement (push, slow, restrain, teleport…)
• status conditions (frightened, blinded, charmed…)
• theme or flavor (holy light, shadow binding, storm magic…)

Example: “A crackling line of radiant frost strikes a single enemy, dealing cold damage and slowing them briefly.”

Spell level

Choose the spell’s level from cantrip (0) to 9th level. The builder then uses the Dungeon Master’s Guide spell damage table to match appropriate damage:

• Cantrip: ~1d10 single-target damage
• Level 1: ~2d10
• Level 2–3: 3d10–5d10
• Level 4+: scales toward 15d10 at level 9

Cantrips cannot be healing spells and normally scale with character level instead of spell slots.

Spell role

This guides both balance and tone:

• Damage – blasting, strike spells, elemental attacks
• Healing – uses the same table as damage but in reverse
• Utility / Control – battlefield manipulation, debuffs, movement, information

Choosing “Utility / Control” tells the AI not to produce direct damage and instead focus on effects like slowing, restraining, teleportation, silence, invisibility, or battlefield shaping.

Primary target pattern

This choice directly affects balance:

• Single target – higher per-target impact, stronger riders allowed
• Multiple targets / area – damage per creature is reduced

The builder automatically adjusts dice output to mirror official AoE damage patterns.

Preferred caster classes (optional)

This field is optional and controls the identity and flavor of the spell. You can list specific classes, or exclude classes if you prefer.

Examples of valid inputs:

• wizard, sorcerer – arcane casters
• cleric, paladin – divine or holy magic
• druid, ranger – primal or nature-themed magic
• anything except bard – exclusion pattern
• not warlock – soft exclusion phrasing also works

If you leave this field blank, the AI automatically chooses appropriate class lists based on the spell’s theme, school, and mechanics.

When you're ready, return to the Spell Builder or explore the saved spell gallery.