The heroes storm the Temple of R’gu, the God From The Stars, to steal the Ruby of the Winged Master
Enter the Kingdom of Frog King in search of Treasure. What deal will you have to strike to get out alive?
Some parallel worlds have different time-flows, like the fabled dwelling-places of the elves: those who visit them under the hill for a night return to find that years have passed in this world. Perhaps it is the gate leading between the worlds which causes the alteration. If a gate were 'misaligned', the shift from '| |' to '| \' or '| /' as it were would lead to that difference, much as a light-beam split and bent by a prism ends up taking a longer path. There might even be a mathematical function linking degree of misalignment to alteration of time-rate.