Hats off to ISlide for finding the glitch all you are doing is interrupting a mantle that results in every mantle from then on taking you to the map co-ordinates of your previous mantle until your game is restarted.
I used the level editor to find maps which share co-ordinates for the purposes of going fast but I'm a bit tapped out on the process now so I uploaded the compiled maps and tool so maybe other people can find faster warps.
The level editor is in Spanish and a bit tricky to use but I made a very basic how to document
thanks for the files
so apparently if I'm not mistaken (EDIT: I checked and it works !), you can save the coordinates of the first big rock of Karum (that you use in the run to warp a some point), and those coordinates are matching with some place near the end of Al Farum, where the two golems are. So it would entirely skip Al Farum. I didn't use this back then because I thought the key was required, and also I had to get the rune.
EDIT:
I can't get the level editor to work: it launches ; I want to open a map file so I use "open", I browse for a .mp file as the "open" window invites me to do, click on it, then LED seems to load it, but nothing appears on screen but a pitch-blue window, supposely the map visualizor, but empty. The console says "Error: no es un archivo de map". Strange.
then rendering the .lvl works, but I don't see the point of navigating the lvl this way, I'd like to see the map (i mean, like a real map)