Spell Synthesis (WIP)

By using certain spells in conjunction, you can cause these spells to “fuse” and create more powerful effects. These effects could range from Evocation spells causing more damage or gaining additional effects, to illusion spells having greater impact/less restrictions.
The idea is that you first cast a spell with a duration longer than instantaneous, then cast another spell during the other spell's duration to create a more powerful effect.
Factors that determine the strength of the fused spell's effects:

• The level that spells need to be cast at - perhaps a spell needs to be upcasted before it can be fused, ie. The spell is 2nd level but needs to be cast with a 3rd level spell slot. Higher spell slots should be more powerful
• Number of spells required - More spells = More power, or perhaps more unpredictability/chaotic fusions
• Can multiple people make the spells fuse? - Each fusion should state whether one person has to use the fusion or multiple people can make it. Maybe if the spells are cast with a higher spell slot than necessary, multiple people could fuse the spells. Typically, single person fusions should be more effective than multiple person fusions, but certain combinations could give the same level of power if the required spells are harder to use together, such as if they are on different class spell lists.
• MORE TO ADD AT A LATER DATE

Synthesis Format
Spell Synthesis: Name of the Synthesis
Synthesis Level: The average spell level of the spell slots used, rounded down. Used mainly for things like Counterspell and Dispel Magic
Synthesisers Required: Specifies the number of people required to create the synthesis. Could be any number, One, Two, Three, or Any
Synthesis School: The best school that describes the synthesis's effect. Not directly linked to the Required Spells.
Synthesis Duration: How long the synthesis duration lasts for, and if Concentration is required.
Required Spells: The spells that need to be cast, in that order and the minimum level spell slot required.
Synthesis Effect: The effect that occurs if the synthesis is successful.

Example Synthesis
Spell Synthesis: Flame Burst
Synthesis Level: Cantrip
Synthesisers Required: One
Synthesis School: Evocation
Synthesis Duration: Instantaneous
Required Spells: Create Bonfire, Flame Bolt
Synthesis Effect: By shooting your Flame Bolt into the bonfire, you cause a reaction that rapidly expands outwards. All creatures within 10 feet of the Bonfire's location must make a Dexterity Saving Throw.
On a Failed Save, they take 2d8 Fire Damage and are set ablaze for 1 minute. They burn bright light for 5 feet and dim-light for 5 feet more, and take 1d6 Fire Damage at the start of their turn. Either they or another creature can use their action to extinguish the flames.
On a Successful Save, they only take half damage.
The initial damage increases by 1d8, and the ablaze damage increases by 1d6, when you reach 5th Level, 11th Level and 17th Level.

Will add a slightly more complicated example later.