Planar Gateway
(Conjuration/Summoning)

Range:  10 feet per level
Components:  V, S, M
Duration:  1 round, hour, or day per level maximum
Casting Time:  Special
Area of Effect:  One gateway
Saving Throw:  None

This spell has the power to open a planar gateway to another plane - no matter where the caster is right now. Thus, it is a highly sought spell. The casting time can become quite prodigious (as you will see) but it can be shortened by a very complicated ritual. This gate is under no one's control and anything can pass through, in both directions. First, the duration of the spell must be chosen by the wizard. The casting time must then be calculated from the planar layer to be reached and the current location of the caster, as follows: a gateway from the prime material to another prime material plane takes one hour of casting time per round open (if the duration was stated in rounds), one day of casting time per hour open (if the duration was stated in hours), or one month casting time per day open otherwise.
From the prime material plane to an inner plane, for every plane or planar layer traversed, multiply by two. From the prime material plane to an outer plane, for every plane or planar layer traversed, multiply by five. From an inner to an outer plane, for every plane or planar layer times traversed, multiply by ten. From an outer plane to an outer plane you need the permission of a god on both planes. Then, the casting time is multiplied by one hundred. As a character can normally only cast for some 16 hours per day the actual casting time will be even longer (unless the character is willing to give up experience levels: see below).
For example, a gateway from the prime material plane to the second level of Hades that is supposed to stay open for 3 days has a normal casting time of 1 month per day open = 3 months, times 5 times 4 (astral, concordant, Hades' first level, Hades' second level) = 3 months times 20 = 60 months or a full 5 years.
The casting time can be reduced: for every experience level offered in the casting, the casting time is reduced by a factor of 1/2 (rounding up) until a value of one is reached. After that, the time can be further reduced by 1/2 if 5 more levels are offered for each further reduction until the minimum casting time of 1 round is reached.
Example continued: we eventually calculated a casting time of 60 months. This can be reduced by one half for every level offered. Thus, if our character offered 6 levels this would be reduced to 30, 15, 71/2 (rounded up to 8), 4, 2, and 1 by halving six times. Still quite long, but manageable. The character still has to be able to cast 9th-level spells after offering those levels, as the levels are drained at the beginning of the casting. Note that this might reduce the maximum duration. As the example above has shown, opening gateways for a long time can take an even longer time or many hard earned levels. As the character has offered the levels voluntarily, they cannot be regained with restoration, but only with a full wish per level lost. Thus, it is not very often that planar gateways are opened from an outer plane to an outer plane, but if they are opened they are opened with a lot of power behind them.
The material components are solidified essence of the target plane, para- or quasi-elemental planes are considered to be one with their parent plane (you would need frozen ice to open a gateway to the plane of water, ice, or sludge), plus a full gallon of blood (or another appropriate liquid) from inhabitants of the target plane.

