The start of this quest is random; you have to fish until you get a message in chat saying you have fished up the Bottle
Once you have fished up the item use your wise glasses to read the message.
You will have to wait 2 Minecraft days (40minutes) to be able to see it, because the letter needs to dry. During this time DO NOT swap servers.
When the time is up you'll be able to read a message that looks like this
Go to Baremaw and talk to Avery
-822, 49, -272
Catch and give 3 Weedle's to Avery
Find Phoenix near a house by the Poke Mart in Baremaw
Hint: use /poi to track the mart
Talk to Phoenix and defeat him in Battle for information
Phoenix will have 6 Random Level 85 Pokemon every battle
Find Mateo at the Baremaw Player Gym and speak with him
-851, 75, -432
Find the 6 Evolution Stones for Mateo
Hint: Get 3 and then go swap to a different gen 5 server and get the same 3
Evo Stone #1
Entrance:
-765, 47, -459
Evo Stone #2
-729, 44, -471
Evo Stone #3
-823, 64, -480
As I said above, swap servers or do /hub and collect the same stones to get all 6
Return to Mateo and give him the stones. Find another local near the Baremaw Pokémon Center.
Speak with Amber, she is standing next to Avery from earlier
-830, 47, -273
Catch up to Amber
-863, 45, -335
Keep on following Amber
-817, 43, -390
Keep following
-754, 47, -455
Find a Baremaw local on the docks of Baremaw, speak to Lane
-833, 44, -247
Speak to Sydney by the House with the Expert Trainer. Battle Sydney
Sydney probably also has a random team every battle, this time of Level 90-95's; defeat her in battle
Find Katherine in Sandgate
Hint: Her House is behind the Pokémon Center
-1109, 48, 131
Meet up with Katherine at the Everhallow graveyard
24, 35, -47
Defeat the Cofagrigus
That's all folks