Fury of the Immortals
space-time rifts and portals
It seems that wherever the Wyrd can be found, so can rifts in space and time. The first time the party encountered such an anomaly was in Corran Keep. Upon discovering the Mirror Shield, an item impregnated with the energy of the Wyrd, it served as a sort of pocket dimension prison for Rheddrian and apparently allowed an aberrant Horrific Floating Brain Creature to pop into their reality. Upon sailing back to Corunglain a wild magic storm in The Broken Lands opened a portal shearing their ship in half and deposting Hideous Crustacean Creatures from another reality. Fleeing, after putting up a good fight and losing two crew, led the part to the Comeback Inn and its basement portal that sucked them 4,000 years into the past to ancient Blackmoor. Surely, Rheddrian's concern that its power could be used to open Mystara to an inter-dimensional invasion is not ill-founded.