Combine

You meld two spells you have prepared and join their effects. The two spell cannot exceed more than 7 total spell levels. For example, you can meld a 5th-level spell with a 2nd-level one, or a 3rd-level spell with another 3rd-level one. You then hold the combined spell's energy for the duration and can release it when you choose. If the combined spell's duration ends before you release it the combined spell dissipates without taking effect.

When you release the combined spell, the most restrictive casting time, range, area of effect, etc., are used. For example if blight and slow are combined the joint spell would only affect one creature, because blight only targets one creature. The combined spell would also have a range of 30 ft. because blight has the shorter range. The casting time would be one action because the spells have that in common. The GM can decide if the combined spell is has the properties of the more favorable spell as they see fit.