Vell is a giant seamonster added to Black Desert in January 24th 2018. Since it is a boss at sea you have to use cannons to damage it so that means only guild ships and Epheria sailboat/frigate that have cannons are used. If you are bringing your own ship it should have at least green gear enchanted to +5 and 30x ship repair materials (bought from the market). When you are sailing on a guild ship all you need is some hp potions so anyone is welcome to join!
He spawns between 1 and 2 gmt and there is a server wide message 30 minutes before he comes out of the sea. To get to Vell all you have to do is sail north from Lema Island into the area Vell’s Realm. Be careful if you are at his spawn location when he comes out of the sea, your ship will get damaged and may sink.
To damage him you will need park your ship between rocks and make sure you have a clear line of fire to the boss, when you have found a good spot make sure to get of the wheel as it makes the ship not able to move and you won´t get pushed around by other ships.
Using the canon
Get onto the cannon by pressing R and hold down left shift and left mouse button and a small bar will appear that charges up usually you want to release between 80 and 100% to make the cannonball fly the max distance.
Three or four times each encounter he will enrage and knock you off the cannon you need to be fast and get back on it or jump off the ship and swim far down, this attack will kill you instantly if you dont watch out. There is good news though: if you die nothing will be lost and you can respawn at his node then swim back to the fleet in the south.