Spell Assimilator

A character sees a spell cast by another magic user, and they want to learn said spell…Now they can, but it won't be easy. 

Spell Assimilation is a unique process for any wizard who wishes to expand their magical abilities. The process can incorporate a lot of elements from artful indulgence to scientific rigor, each wizard has their own flavor. However it is done it follows the following steps…

Perceiving a Caster at Work 

Many spells create obvious effects: explosions of fire, walls of ice, teleportation, and the like. Other spells, such as charm person, display no visible, audible, or otherwise perceptible sign of their effects, and could easily go unnoticed by someone unaffected by them. As noted in the Player’s Handbook, you normally don’t know that a spell has been cast unless the spell produces a noticeable effect.

But what about the act of casting a spell? Is it possible for someone to perceive that a spell is being cast in their presence? To be perceptible, the casting of a spell must involve a verbal, somatic, or material component. The form of a material component doesn’t matter for the purposes of perception, whether it’s an object specified in the spell’s description, a component pouch, or a spellcasting focus.

If the need for a spell’s components has been removed by a special ability, such as the sorcerer’s Subtle Spell feature or the Innate Spellcasting trait possessed by many creatures, the casting of the spell is imperceptible. If an imperceptible casting produces a perceptible effect, it’s normally impossible to determine who cast the spell in the absence of other evidence.

Identifying a Spell

Sometimes a character wants to identify a spell that someone else is casting or that was already cast. To do so, a character can use their reaction to identify a spell as it’s being cast, or they can use an action on their turn to identify a spell by its effect after it is cast.

If the character perceives the casting, the spell’s effect, or both, the character can make an Intelligence (Arcana) check with the reaction or action. The DC equals 15 + the spell’s level. If the spell is cast as a class spell and the character is a member of that class, the check is made with advantage. For example, if the spellcaster casts a spell as a cleric, another cleric has advantage on the check to identify the spell. Some spells aren’t associated with any class when they’re cast, such as when a monster uses its Innate Spellcasting trait.

This Intelligence (Arcana) check represents the fact that identifying a spell requires a quick mind and familiarity with the theory and practice of casting. This is true even for a character whose spellcasting ability is Wisdom or Charisma. Being able to cast spells doesn’t by itself make you adept at deducing exactly what others are doing when they cast their spells.

Assimilating the Spell

If you successfully identified the spell during battle or during social interaction, you have 30 minutes to complete arcane scrutiny. You can only complete arcane scrutiny on a spell that is on the wizard’s spell list and must be a level that you can cast. If a spell is upcast to a higher level of spell than you can usually cast, you can complete arcane scrutiny, but it will be more difficult. 

During this period, you’re looking more keenly into the specifics of the spell effects, for any residual materials used, recalling all components, and, finally, transcribing all of this information. The character makes an Intelligence (Arcana) check with DC equals 10 + the spell’s casting level. If the spell is cast as a class spell and the character is not a member of that class, the check is made with disadvantage. For example, if the spellcaster casts a spell as a wizard, all classes that are not wizard have disadvantage on the check. The time it takes to complete arcane scrutiny is 2 minutes multiplied by the spell level if it was cast by a wizard, and 3 minutes multiplied by spell level if it was cast by someone other than a wizard. 

If you are unable to complete arcane scrutiny during the 30 minutes after the spell was cast or you fail the skill check, you are missing an untold amount of information. You may still try to complete arcane scrutiny, but the risks are unknown (up to the DM’s discretion). You cannot complete arcane scrutiny after 24 hours of the original spell being cast. 

When you have completed the arcane scrutiny of a spell of 1st level or higher, you can begin the experimentation phase of the assimilation. 

Finalizing the actual spell will make it into your spellbook involves reproducing the basic form of the spell, then deciphering the unique casting technique of the original caster. You must practice the spell until you understand the sounds or gestures required, then transcribe it into your spellbook using your own notation.

For each level of the spell, assimilating the spell takes 4 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. 

You must finish assimilating the spell within 7 days of completing arcane scrutiny.

Once you have completed all the above steps, you can prepare the spell just like your other spells.