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From the Kickstarter Page:
Time Heroes, in its default setting, is about stopping the evil sorceress Morgan la Fey from altering time as we know it.
Morgan la Fey has come to a point in history where magic has long since died but before technology has evolved to completely replace it (basically, the present). She has torn open rips in the fabric of space and time to draw through armies from the past and future with which she intends to make the Earth her own. She has managed to place a time bubble around a few year block that has been separated from the normal passage of time. Her goal is to take control of the planet, send people back and then drop the bubble, altering the course of history in one fell swoop.
The Great Merlini, last living descendent of Merlin has gone from simple stage magician to discovering the power of his ancestor within himself with the assistance of his ancestor’s book of magic, the Bionomipro. He is using this power to draw his own people through time and space in order to hold back la Fey's ambitions. While the bubble around the present allows la Fey to bring people through without repercussions, it also prevents going back to alter events that have already happened within the bubble itself. Essentially, if Merlini can keep Morgan la Fey at bay for a few years, the bubble will drop and normality will be restored.
So that's the basic lore behind the setting. But how do I see this play out in the game itself?
Time Heroes is meant to be a zany romp for a group of players. Ultimately, I envision it along the lines of a television show or cartoon where, though there may be arcs here and there, primarily each session is its own episode and - much like, Inspector Gadget, for example - Morgan la Fey will always barely slip away at the end of each "episode." Obviously the reasoning behind this is because if she's taken out completely, any series would be over. Also, she will be almost entirely in the background pulling strings and not in the thick of it herself. I want the world of Time Heroes to be one in which a sword-carrying barbarian, a laser mop-wielding space janitor and a Spam salesman are all equally likely as character concepts, even in one group.