well... to kill some time before my better half and I head into DC and fight a million people for a good seat for the fireworks hahah. Here is what I am thinking as far as the spell.
The spell uses the flows of the Radiance which are confined to Mystara (if I am not wrong) yet are all over Mystara thus making the spell only usable between points on Mystara.
Skimming
by Michael BerrySpell of the Radiance
Skimming (Spell Level 9)
Range: 30'
Duration: One Turn per level of the caster
Effect: Opens a gateway to another point on Mystara
This spell allows the caster to open a gate to any point on the surface of Mystara. The point must be a location the caster knows well. The caster having 'general knowledge' per the guidelines of the 5th level Teleport spell. The gate serves as window allowing one on either end to see through the gate to the opposite side. Spell effects can be felt through the gate yet spells can not be cast through the gate itself. The gate itself can be ended by the caster at any time during the spell's duration by command word. Use of this powerful spell though has a risk. In addition to the 1% chance of having a part of the body corrupted by using a spell of the Radiance, the amount of Radiance this spell uses increases the chance of corruption to 10%.