Adventurer Summoning (d20)

From the introduction:

A mini-adventure for four 10th to 12th-level player characters...The PCs are currently in Dragonspur City or wherever they were last, doing whatever they were doing last, although they should have sufficient time to rest, memorize spells, and heal up from their last escapade. They will need their strength for what lies ahead. When they are all together, they suddenly feel a strange sensation. There is a blinding flash, vertigo strikes them, and when they regain their senses they find themselves in a strange scene...