The addon is a java mod that was ported to bedrock with the permission of the original author who is fish0016054, the addon adds a variety of mobs, items and blocks that we will see in each update of the addon.
Select version for changelog:
Changelog
Removed the piranha, swarner and ptera.
Added the unburied and undertaker.
Loot added to mobs.
Mob models have been improved.