The following explanation on time and inter-dimensional travel is taken from the Appendix to “The Chronicle of the Hero Volume 1”Elannort, Year of Creation 50508 by Kris the Bard.
“Now, I’m no expert on inter-dimensional or time travel, but I’ve acquired some experience of it recently, ever since I was bitten by the rat at the Battle of Elannort, which turned out to be Fate, which implanted the gene that enabled me to journey with the Hero.
There are two types of travel involved here and two mechanisms for travelling. There is simple travel between the dimensions and there is travel backward or forward in time either within a single dimension or across dimensions. Time travel can only be achieved by using the portal on top of the High Tower at Melasurej or, I believe, on top of the Lost Tower. It is possible that a third tower with a portal also exists in the city of Illium. These portals can also be used for inter-dimensional travel. The most common means of inter-dimensional travel, though, are through dimension portals. These are located just about everywhere, but only link any two dimensions. Some dimension portals are fixed, but many are in a state of flux. This means that getting from your dimension to another specific dimension may take you through any number of other dimensions. Navigating dimension portals is a particular skill and I have only known one individual, Jhamed al Suraqi, who is expert in this art.
Unfortunately travel through the dimensions and indeed across time is limited to very few people. The firstborn (elves, dwarves, and the now almost extinct race of men who were here before humans) together with wizards have the innate ability to make these crossings. Very few humans possess the ability and it appears to be a genetic trait that provides the power. The Everlasting Hero always has this ability.
The multiverse also protects itself from too many paradoxes by limiting what inanimate objects can travel through time and the dimensions. With a few exceptions, one being the Hero’s Sword, nothing can be taken back in time. This is why persons travelling back in time arrive naked. (Please don’t ask me about things like medical implants, there have been no reported cases yet.) There appears to be a similar prohibition when travelling forward in time. On the other hand, travelling through the dimensions is a lot less waring on one’s privacy. Any inanimate objects that one is in direct contact with make the transition but no living things can pass through, unless they have the correct genetic make-up.
To make things even more complicated, time seems to pass at different rates in the various dimensions of the multiverse. FirstWorld is at the centre and it is here that time travels slowest. It is therefore useful to measure time based on the FirstWorld calendar. Whenever a person travels in time, spends one month in the past, and is returned to her own time because of a paradox, she returns one month later than she left – in other words, a person’s own time line and age is maintained. Similarly, if a person spends one month in the future and is ejected from the time stream, he returns to a point one month after he left. The only way this rule can be violated is to use the time portal at both ends of the journey. However, if a paradox has been created, at least one new dimension of the multiverse will have been created and there may be two versions of the person in different realities. Travel through the dimensions is more problematic. Let’s keep it to just two dimensions, otherwise it becomes horrendously complicated. If someone spends a month in a dimension where time is running at twelve times the speed of his home dimension; when he returns to his dimension, only about three days will have passed. On the other hand, if a person spends a month in a dimension where time is running twelve times slower than her dimension; when she returns to her dimension, a year will have passed. A person ages at the rate that time passes in the dimension in which he or she is present. If I’m aged 21 and I spend one year in a dimension where time passes five times more slowly than my own, when I return to my own dimension I will be 22 years old, despite five years having passed there.”