Cobblemon: Legends Untold

This datapack/mod adds 8 Legendary, & 1 Mythical Pokémon, 5 structures, & 7 new items to cobblemon.

for example

New Legendary (And Mythical) Pokémon & How to get them  

Rayquaza is found in the Sky Pillar, a new rare structure that you can find in mountian biomes. Bringing a Jade Orb to the top of Sky Pillar will spawn in a level 70 Rayquaza. Rarely in some structures you will find a Jade Orb or a Jade Map, a map that leads you directly to Sky Pillar. Every player on the server will get only one chance to catch Rayquaza.

Mewtwo

Rarely in Legendary Structures like Sky Pillar you will find a new item called Mew DNA, using this & a nether star or a comet shard you can create Mewtwo in a Resurrection Machine.