[quote=@Bishop]
Well we're not in canon, there wasn't any death trooper that believed in The Emperor like a maniac, our characters didn't exist. There was no Heavy Trooper Named Di that killed Jedi. It doesn't have to exist in the Star Wars universe for us to use it. The whole planet will be made up so why not add this artifact? The rebels could have secretly build a base on this planet, hidden for many years, just to study the structure. And as we pass near the planet they want to try out it's power for the first time. We're the practise target. In the end its about having a fun and unpredictable adventure.

Also, they built a Sun Crusher. What's the problem with a pyramid shaped structure destroying one Imperial ship that happens to pass near the planet?
[/quote]

Just because we're not in canon doesn't mean that we can just come up with random shit that makes no in universe sense.

The Rebels do not nearly have enough resources to create a giant sun god temple laser, they barely have enough to keep running from the Empire. Unless the entirety of the Rebel high command had a stroke and thought it would be best to waste resources on creating a mini notDeath Star, there can't be such a project. The RA doesn't have enough supply or manpower and even if they did, why the fuck are they building it on a planet in the middle of no where? Why not build it in space? Why not just do the more tactically sound option and not build it and use those resources and man power in places they could use them like making hidden outposts and sending out more agents and soldiers to do guerrilla war on the Empire?

The issue with you "we're not in canon so it doesn't matter what happens what we do" claim is that while yes its most likely what we're doing never happened in canon, its still relatively plausable. Most if not all of the troopers we made are grounded in enough canon that they could be canonical and super star destroyers going through out space isn't that far fetched. Saying that the rebels would divert precious resources and man power to construct a weapon on a remote planet where it'd probably not see much action is just impossible as the rebels' situation in canon. The Empire needed several world's worth of resources and slave labor to make their Death Star and I'd suspect that the Rebels would need significant logistical capibilites they lack and manpower that would basically require slave labor too to build something like your sun temple cannon, not exactly good for rebel propaganda now is it?

[@Azkott] I have a far simpler and more logical way to say how the ship got kerfucked.

In a previous stop/shore leave, several rebels jumped a pack of storm troopers, took their equipment and got on board the ship. They then proceeded to get to the hyperspace drive and fuck with it just enough that once the SSD would take off with its escort of other ships, our Super Star Destroyer would come out of Hyperspace jump early around some random planet. Once the ship was out of hyperspace, they'd blow the rest of the ship's systems leaving just enough systems to force it down planet side and make a smooth crash landing that wouldn't blow up the ship. 

This concept would make it so that there is a plausible excuse for why the ship got fucked up and had to land (remember, SSDs aren't meant to be anywhere but space) while also giving our characters enough of a chance of survival (wether by escape pods or pure luck) to get it down to relative safety. Then its discovered that there is in fact a rebel based on the planet and that the rebels who snuck on board actually were aiming to get the ship to this planet to try and loot its stuff for supplies.

Such an explanation would also give proper reasoning as to why and how our ship ended up all alone instead of being surrounded by other Imperial vessels which is what would certainly happen most of the time.