Time travel! My bread and butter. Oh, let me count the ways I've used it...
1- A death knight in Ravenloft is playing with a time orb. Its unstable effects spread across the countryside the PCs are journeying in and *whap* send one of the party into the near future, where he sees an attack by manticores. The adventure proceeded and the party was indeed attacked by the manticores. As the adventure continued, two or three more times a different PC was shifted into the future. One saw the future selves attacking the death knight in his castle's audience chamber (and see a fellow get stabbed through the back!) and another was sent farther along into the future to see the party enter a chamber where a statsised elf stood in a pale shaft of light and the NPC triggered a trap before the PC returned to the present. This latter bit was made up without knowing what it meant but it turned out to be one of the key moments in escaping the Demiplane of Dread. All in all, a cool module where time distortions were a neat effect and not the module's premise.
2- I took my Realms campaign to WAR! Thay banded together with a group from Kara-Tur which possessed psionic statuettes that fanned the embers of racial hatreds into infernos. Thay, the Krie'lat (the oriental group), and their githyanki and red dragons allies swept across the Heartlands, pushing the PCs steadily westward. They eventually ended up in Waterdeep where they learned that the psionic statuettes each contained a psionically charged orb. The psionic stone was created when two "feuding" archmages destroyed themselves far beneath the earth to the south of Waterdeep. To keep this long story short, one of the City of Splendors' noble families (Brokengulf) possessed a time device. The PCs used it, and the knowledge they'd attained in previous adventures, to go back in time and stop the wizards from destroying themselves. The situation became quite murky when the archmages' true goal in the Underdark was discovered--destroying a mind flayer community and its elder brain. Could the PCs honestly stop the wizards from breaking the staves of power (retributive strike)--one action leading to the war-torn future and the other allowing the mind flayer community (already poised to attack the surface) survive? They did in fact stop one of the staves from being broken and that turned out to be enough as a return to the present revealed no all out Realms war. *whew*
This timeline resurfaced, however, in a later module when the time device of the noble family (now the PCs' home) was destroyed. The blast shifted the party into an alternate timeline where the Thayan, Krie'lat, githyanki alliance defeated all in their path. A resistance spurred on by Corymr was about to make a counterattack against Darkhold--a bad guy fortress--when the PCs arrived. The details are vague in my mind, but I believe the goal was to assist the resistance movement in exchange for magical passage back to Waterdeep. The PCs were victorious and, to return to their own time, destroyed the alternate timeline's time device in the same way it was destroyed at the adventure's beginning. The result was a temporally displaced noble villa and a goodly amount of gold still unaccounted for.
3- More recently, in another Realms campaign, the planet is about to come under devastating attack by a Dragonstar-ish weapon capable of hurling meteors at a planet to cataclysmic effect. The BBEG is none other than Orcus! His followers have been slaying a planet's population and then turning them into undead for the Demon Prince's vast army. A wizard from that cataclysmic future arrived in a previous module to warn of an unnamed threat. He then returned in a module we played only last Sunday to reveal what the threat really is! He brought along an object from the future and asks the PCs' aid in deciphering it. The item is a "chronostone" and, due to magical things going on to improve the party's lair, it reacts badly to the protective magics in effect and transports the PCs to the near future--after the bombardment of meteorites!
The party is picked up by a space ship, piloted by those who are searching for more powerful vessels hidden years ago by a colleague on Toril. By the end of the module, the PCs discover the combat ships and learn the rudiments of piloting them before blasting off to attack Orcus' weapon still orbiting the planet. However, the party is unsuccessful as a half dozen demons teleport into the engineering section and destroy the ship's power systems. The meteor thrower's unmanned defense ships blow apart the PCs own vessel. The blast destroys the ship and, by the same quirk that brought them to the future, causes the "chronostone" to send them back to the module's beginning. The chronostone is quite ruined, but the PCs now have the knowledge to stop the weapon--where the futuristic ships are, how to use them, and what guards them and the meteor thrower. Only time will tell if they're successful...
