Combination Casting (EAFW)

Elemental clerics may combine their powers to access the spells of the paraelemental planes. This is known as combination casting.
Whenever two priests of different elemental schools need to cast a paraelemental spell, they choose the spell they wish to cast and then follow the conditions listed below. Only elemental clerics with major access to earth, air, fire, or water may perform combination casting. Druids and templars may not perform this feat Conditions for casting are as follows:
* The priests must be in contact with the paraelements, or with each of their own elements, and must be in physical contact with each other, by joining hands for example.
* Both priests must perform whatever somatic, verbal, or material conditions are required for the spell.
* The spell's casting time is doubled.
Once cast, the spell activates as if it were cast in the normal manner. If one of the priests is of a higher level than the other, the senior cleric determines the specifics  of the spell—who or what is targeted, and any other information required for the casting. The effects of the spell are based on the lower level cleric.
Adverse spell effects (such as the spell being reflected back onto the casters), will affect both clerics, no matter how many targets the spell was directed to attack.
Finally, priests may only cast a number of spells equal to lowest level cleric's slots for his level. This "spell pool" is refreshed after a day.
Example: Herak is a 9th-level fire cleric, and Telia is a 7th-level earth priest. They want to combine powers and cast a spell of the Paraelemental Plane of Magma.
Since they are standing in a rich field, Telia is in contact with her element, but there is no fire. Herak casts resist fire on himself and Telia, and then creates a magical fire to surround them. The first condition is met.
Herak and Telia briefly discuss which enchantment to employ, and decide to use the eruption  spell. The clerics link hands, point their fingers at a small patch of earth, and watch as a great flow of molten rock erupts from the ground. Since eruption is a 4th-level spell and Telia is of a lower level than Herak, they will not be able to cast any other 4th-level magma spells this day. They could, however, cast two more 3rd-level spells and three 1st- and 2nd- level spells, according to the spell slots available to Telia's level.
The damage and effects will be based on Telia, since she is the lower-level cleric. In the case of the eruption spell, this means it could do 7d6 points of damage, but Herak would decide on the target.