Ringlerun’s spell research leads in unexpected directions as he unintentionally creates a flying gelatinous cubelet.
When creating a new spell, use existing ones as examples. Here are some things to consider:
Name. The spell must have a unique name.
Balance. If the spell is so good that a caster would want to use it all the time, it’s probably too powerful for its level.
Identity. Make sure the spell fits with the identity of those who can cast it. Sorcerers and Wizards don’t typically cast healing spells, for example.
Spell Duration, Range, and Area. A longer duration, greater range, or larger area can make up for a lesser effect, depending on the spell.
Utility. Avoid spells that have very limited use, such as one that works only against Oozes. Few characters will bother to learn or prepare such a spell.
For any spell that deals damage, use the Spell Damage table to determine approximately how much damage is appropriate given the spell’s level. The table assumes the spell deals half as much damage on a successful saving throw or a missed attack. If your spell doesn’t deal damage on a successful save, you can increase the damage by 25 percent.
You can use different damage dice than the ones in the table if the average damage is about the same. For example, you could change a cantrip’s damage from 1d10 (average 5.5) to 2d4 (average 5), reducing the maximum damage and making an average result more likely.
You can also use the Spell Damage table to determine how many Hit Points a healing spell restores. A cantrip shouldn’t provide healing.