The Planar Cartographic Library Annex of Amber

various methods of travelling from star to star are well-known.
while NOT the favorite of Amberites, too easy to die of suffocation
in the airless void of deep space, and many other hazards ;
but shadowalking from & to those many star worlds is reasonably easy.

www.alternityrpg.net/

and

en.wikipedia.org/wiki/Planets_in_science_fiction

and

a good variant explaination of the multiverse can be found here ;

tvtropes.org/pmwiki/pmwiki.php/Main/TheMultiverse

and this explains some of the weird alternate verses ;

tvtropes.org/pmwiki/pmwiki.php/Main/AlternateUniverse

Gor is one of the most evil worlds, full of slavery and brutal BDSM against women.
the world is ruled by void-space aliens that will not allow any advancement
in literacy or technology or freedom among the naitives and inhabitants.
because of all the raiding and brushwar fighting, it is one of the most dangerous worlds
to visit.

en.wikipedia.org/wiki/Gor

and

gorchronicles.com/

and the map ;

thecrucibleofgor.weebly.com/maps-of-gor.html

Of course, since this is Amber, a lot, or most, of those weapons won't work outside of the shadow they are from. Unless an item is powered by Pattern, Logus or Trump (or a Spikeard) the odds of it working in other shadows seems to drop dramatically the more powerful the item is in its home shadow. Swords work almost everywhere, but a nuclear bomb probably only works on Earth. A super powerful magical equivalent of a nuke probably only works in its home shadow. The less powerful an item is, the more likely it'll work in shadows further away from its home shadow. And in game terms, only those that the character pays points for will work (almost) everywhere. 
  
If such items worked everywhere then all of the elder Amberites and Chaos Lords would have them by now. Corwin wouldn't have had to go to all the trouble of finding a way of getting guns to work in Amber in the series, if there were very powerful and deadly shadow magic items that he could get that would have helped him take the throne. And the Courts of Chaos would have been using lots of them in it's war against Amber if such items could be used. A logrus user would just have to reach out with his/her tendrils and spend a few weeks to get anyone of those super deadly items for free (with no risk to themselves), but the reason they don't is that the items won't work (or be anywhere near as powerful) when they are removed from their home shadow (again unless the character pays points for it and makes it "real", and super deadly items cost a lot of points, so only elder amerites and chaos lords would be able to "afford" them). 

So a super deadly "Sword of Doom" that does deadly devastating damage and can kill anything in it's home shadow, might just be a cool looking regular sword anywhere else out in shadow unless it is powered by Pattern, Logrus, trump or points are paid for it. . 

. . . . if you don't mind having your head explode with MATHEMATICS that mankind was not meant to understand . . .

en.wikipedia.org/wiki/Mathematical_universe_hypothesis

and

en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_of_Mathematics_in_the_Natural_Sciences

and

arxiv.org/abs/astro-ph/0407329

and

space.mit.edu/home/tegmark/toe_frames.html

and

www.space.com/31465-is-our-universe-just-one-of-many-in-a-multiverse.html

and

www.math.columbia.edu/~woit/wordpress/?p=5907

and

www.thoughtco.com/multiverse-definition-and-theory-2699273

and

www.telegraph.co.uk/science/2018/03/18/stephen-hawking-leaves-behind-breathtaking-final-multiverse/