Storm King's Thunder
"Combining the Elements, one can form one hells of spell!"
-Recalled by Almore the Bannered during his eastern travels.
Spell Synergy, or the combination of two spells, is the most powerful form of casting, and requires two or more spell casters.
Spell Synergy compliments the two spells, and creates a single spell merging the two. Once done, the spell is added to the Synergy List planting the synergy spell as one discovered by the party.
Casting a Synergy Spell
To cast a synergy spell, the character's doing it must declare that they are casting the spell at the start of the first character's turn. The second then must agree that they wish to follow along with this plan. The Synergy Spell then activates at the start of the last character in the Synergy Spell's turn. Casting a Synergy spell requires a full-round action.
Synergy Spell Effects
Synergy Spells make the spell more powerful, and the difficult check to surpass it more difficult.
When a synergy spell is performed, the damage of the two spells is combined, along with the damage types. A creature attempting to surpass the spell damage type's must be resistance/immune to both types of damage the spell is dealing before the resistance/immunity is applied. However; their is an exception: If a creature is immune to one of the spell damages, they become resistance to the synergy spell.
The difficulty check of surpassing the synergy spell is 8+ the proficiency modifier of the spell caster who began the synergy spell process + the modifier of the second spell-caster.
The save attribute is determined by the spell added to the synergy spell by the first spell caster who initiative the synergy.
Any additional effects added to the Synergy Spell are determined by the DM.