Spontaneous Casting

This article relates to Teramore's Homebrew magic system, and can be ignored by any character/player using standard caster class/rules, including when using Mana in place of spell slots.

What Is Spontaneous Casting?

Spontaneous Casting is a powerful and flexible approach to magic. Instead of relying solely on pre-prepared spells or traditional spell lists, characters with this ability can invent and cast spells on the fly. This allows for greater creativity and adaptability in gameplay.

However, with such freedom comes cost. Characters who use Spontaneous Casting—either as a replacement for traditional casting or in addition to it—must accept flaws or debuffs determined by the DM. These are personalized and intended to balance the increased magical potential.

Spontaneous Casting is gained in one of two ways: by taking a specific feat or by choosing the Aethermancer class.

Note of Caution

Spontaneous Casting is a ruleset that requires a significant level of trust between a player and a DM. Exploring spontaneous magic will run into many underlying concepts of magical theory and lore in Teramore, and the player will not always understand why a spell fails to work in the way they intend. They need to be able to trust that the DM has a set of consistent rules under the hood.

Likewise, the DM needs to be able to trust that the player is more interested in the utility and roleplay of this system, rather than abusing its potential to power-game. The downside of these rules is they are potentially game-breaking. The design intent is to allow freedom and creativity within a hard magic system.

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Gaining Spontaneous Casting

Feat-Based Spontaneous Casting

Characters may take the Spontaneous Caster feat to supplement their existing spellcasting. When this feat is taken, the character chooses one spell school and gains Rank 1 in that school. This allows them to spontaneously cast spells from that school up to 1st level, using a system of improvised casting governed by Conjure Checks (explained elsewhere).

Each time the character levels up, they may increase their Rank in that school by 1, to a maximum of half their character level (rounded down). The maximum spell level a character can spontaneously cast is equal to their current Rank in the school.

A character may take this feat more than once, selecting a new spell school each time. However, at each level-up, a character may only increase two Ranks total, even if they have multiple schools. These two Ranks may be split between different schools or invested into the same one, as long as each individual school does not exceed the half-level limit.

Every time a new Rank is gained—whether by feat or level-up—a new flaw is applied by the DM. These flaws are not drawn from the standard 5e background list, but are tailored to the specific character and their narrative. They may represent instability, mental strain, corruption, or other story-driven drawbacks of wielding such unbounded power.

School Restrictions

The impact of oppositional magic on character progression

In this magic system, each of the twelve spell schools has a paired opposite. These oppositions represent fundamental contradictions in magical philosophy, theory, and practice. As a result, a character’s selection of schools for spontaneous casting is limited by these inherent conflicts.

Initial Selection

When a character gains their first spell school (typically by taking the Spontaneous Casting feat or choosing the Aethermancer class), there are no restrictions. However, once they choose a second school, that decision locks in limitations based on magical oppositions.

Choosing an Opposing School

If a character chooses, as their second school, the paired opposite of their first school, they are making a deliberate and difficult choice. In doing so, they bind themselves to a dualistic magical path.

• They become locked into those two schools.
• They may continue to increase their Rank in either of the two schools.
• They may not take any additional schools in the future.

This path represents a full dedication to understanding both ends of a magical polarity, and is often thematically rich but strategically narrow.

Choosing a Non-Opposing Second School

If instead a character selects a different school (not the opposite of their first), they take a broader but more fractured approach to magic.

• They are permanently barred from selecting the opposite of any school they have chosen.
• This includes the opposite of their first school, the second school, and any additional schools they take later.
• They may continue to add new schools (within this growing web of exclusions), and increase their Rank in any they already possess.

This approach trades depth for variety, but with accumulating restrictions.

Example 1: Oppositional Commitment

A character selects Luxomancy as their first school. For their second school, they choose Fabrimancy, which is its paired opposite.

• From now on, they may only Rank up in Luxomancy or Fabrimancy.
• They may not select a third school at any point in their career.

Example 2: Broad Access with Locked Gates

A character selects Cerebrumancy as their first school. They later select Biothaumaturgy as their second.

• They are now barred from selecting Spectromancy (the opposite of Cerebrumancy) and Thanaturgy (the opposite of Biothaumaturgy).
• If they later choose Nexumancy as a third school, they also become barred from Transiturgy, its opposite.
• Over time, each school they add reduces the pool of others that remain available.

School Opposites

Spell School	Paired Opposite
Luxomancy	Fabrimancy
Biothaumaturgy	Thanaturgy
Sortisism	Anarchionomy
Nexumancy	Transiturgy
Cerebrumancy	Spectromancy
Aether	Null

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Class-Based Spontaneous Casting: The Aethermancer

The Aethermancer is a full spellcasting class designed around Spontaneous Casting from the ground up.

Unlike other casters, an Aethermancer does not use a spell list. Instead, they gain access to all twelve spell schools as potential domains of magic, and can gain Ranks in any of them without needing to take feats.

At each level, an Aethermancer gains two Ranks, which can be assigned to any combination of the twelve spell schools. The only limit is that no single school may have a Rank higher than the character’s level.

Aethermancers are not required to take flaws for their Ranks. However, they are restricted in other ways: they cannot cast traditional spells without first creating them through gameplay. This process includes practicing and refining a spell until it becomes either an Emergent Spell or eventually a Codified Spell. See Conjure Check for more details.