Alright, so, the Spore Drive.
There is this magic fungus, it has a fancy name that loosely means 'first plant star traveller', the important thing about this fungus is that it primarily lives in subspace, forming a massive multiverse-spanning mushroom ring which pokes little mushroom protrusions into real-space to release spores and reproduce, much like a normal mushroom except in subspace. The Spore Drive works by jumping into the magic subspace fungus dimension and then jumping out back into reality at the desired location. The problem is that the jumping is 'probabilistic' which apparently means that the longer the jump, the greater the number of possible exit points. This is a problem because the network is so fuckin huge that the number of possible exit points becomes incomprehensibly vast and impossible to sift through within milliseconds, and the ships had insufficient computing power to figure out the desired exit point before the native magic subspace fungus ate the invader.
Fortunately, they found a magic alien tardigrade that existed in multiple dimensions at the same time, was probably sentient and had a symbiotic relationship with the magic subspace fungus by just grabbing some fungus DNA and jamming that shit into its own genetic code, which worked because magic alien tardigrade. Because the tardigrade is both magical and multidimensional, it naturally has the innate ability to perceive and navigate through higher dimensional physics, as well as the ability to navigate the magic subspace mushroom ring to teleport around the multiverse at-will. So they jacked the magic alien tardigrade into their computers and used it to do the calculations, boom! Point to point teleportation.
Unfortunately, the magic alien tardigrade didn't take well to this treatment, and it turns out jacking it into computers and forcibly using its mind as a navigation computer was literally destroying its brain with every use. Fortunately, the magic alien tardigrade was able to just jam other creatures DNA into itself, so logically it should be fine to just jam some magic alien tardigrade DNA into a human. So they did that and bam, the human gained the same ability to perceive and navigate higher dimensions as well as the magic subspace mushroom ring, with the minor side effect of progressive neurological damage from having his brain used as a navigation computer and ending up existing slightly outside of conventional space\time, making him a bit loopy. Fortunately the magic subspace mushroom ring can store minds, so when his brain inevitably burned out his mind just hid out in the magic fungus dimension and the crew were able to track him down, fix up his body and shove him back in it A-OK.
In short, the Spore Drive works because of magic subspace fungus and magic alien tardigrade DNA. On the bright side, it has never needed to have its polarity reversed, so that's something.
