This picture follows the events of https://derpibooru.org/images/3250276 and https://derpibooru.org/images/3250845:

Remember how Spike accidentally discovered Thorax hiding in the caves near Mount Everhoof just outside the Crystal Empire's borders? Well, that didn't happen this time around. Seven humans were forced into the world of Equestria to be their salvation, they were the key... but nothing went right. The world was a myriad of whispered lies while the wool was pulled over their eyes and graves had been left unmarked.

Now, there's a reason their world is changing. The whispers have stopped and the world moves on of its own volition.

As for Thorax, he still found his way to the caves of Mount Everhoof, but so did something else. A dark ooze concentrated with Hopeless Magic. It came to destroy their world, but now left stagnant, what damage can it do when exposed to a harmless changeling? A changeling who only wants a friend but is rejected by his hive and is still feared by all the other races. Such a sad creature who is at war with himself and starving... but just found two wounded Wonderbolts taking refuge in his caves for protection from a deadly storm trapping them all inside.