This spider originated from some official concept art from Minecraft Legends. It was likely going to have the gimmick of being able to climb walls but was replaced by the Brilliant Beetle. The reason for the change was likely because of the spider's inherent creepiness. Besides, the beetles can glide.

Concept Art:
latest (1366×768) (nocookie.net)

(DISCLAIMER: Don't try riding this spider, especially at night)!

Feel free to use this spider! I'd love to see them made into an actual friendly mount! I only ask for a simple credit.