cheese it:
dig under one of the unbreakable trees; raise the ground (you will actually be inside the tree at this point)
drop a workbench
use stagbreaker to attack through the tree and hammer him to death!
only thing that will hit you will be poison cloud...if he uses it; which he often wont at such close quarters; but if you stock up on poison potions that wont be an issue.
you can also go upwards; build a platform up a tree above his head height and just shoot him from the comfort of the the platform.
both methods work; the stagbreaker one might be a bit faster and less costly in materials for arrows and bow repair etc

Put down a portal a safe distance away. This lets you flee to repair/heal and come back. If you return promptly his hp won't recover much. When I fought him there was an existing tree house that was high enough that his swipes couldn't reach me. With poison resist potion I killed him with about 150 frost arrows and what little poison I took barely exceeded my hp regen.

We went back in and found an nice tree high enough to shoot him and use iron sledge.. took 30 min but we finally killed him.... thanks for all the ideas
Its harder to do with the stamina drain the way it is

What you need:
-Poison, Health, and Stamina Pots
-Flatten the Ground with Hoe
-Iron Mace (fully upgraded)
*unless you sort of "cheat" and get Silver early on for Frostner, that weapon will kick his ass.
-Iron Sledge (for random enemies)
-Stamina Foods (Muckshake)
-Shield optional as you should dodge all Bonemass attacks instead.
-When Bonemass pukes, do not run away from him, run behind and past him a bit, he will miss.
-Dodge all his attacks, pretend he's just a stinky Troll.

He's not terribly destructive to the environment either so building some barricades walls or floors should help.

Same tactic as every boss: Load up with a ♥♥♥♥♥♥♥♥ of the best arrows you can, then keep distance and shoot arrows at it until it dies. With Bonemass if you are two people it can also help if one person runs in and gets a few hits in with a blunt weapon from time to time

its weak to blunt, and you have a potion to negate poison.
also weak to cold but the frost arrows are next biome, some go for that.
you can raise terrain and make him come at you in a narrow gap, so its you and him with all his spawns stuck outside.
and for the ultimate cheese you can portal in and out to heal up at home or wait out the CD on your mead etc.

Drink poison potion and just fight him with a mace super easy

Mace and frost arrows

Bonemass patern is simple:

- he summons minions
- he punches you
- he makes his special poison cloud

The poison cloud is what you want to avoid the most, even with poison resist mead.
The punch you can parry very easily leaving you some time to do big dmg bonus.
His minions should be dealt with first but as far from the boss as possible.

Rinse and repeat, easiest boss fight in this game but the most fun too imo.

Needless to say to bring a blunt weapon and poison resist mead here. Have fun with your new Bonemass insanity power after that !!!

Iron Mace, 2 hp foods and a stamina food, poison resist potion.

Pop the potion before engaging as it does nothing if the poison is already in you. You can tank all the poison with the potion, use a shield to parry the one melee attack it has or roll it and deal with the adds as they come.

Yea his pattern you can get 2 to 3 hits in with a mace and run out. He is weak to blunt damage. Poison Resist is a must tho.

Originally posted by bigsapling:

Iron Mace, 2 hp foods and a stamina food, poison resist potion.

Pop the potion before engaging as it does nothing if the poison is already in you. You can tank all the poison with the potion, use a shield to parry the one melee attack it has or roll it and deal with the adds as they come.

I prefer to roll. Since H&H, he can do piercing damages (through the shield). Even with a perfect parry, i get about 30-60hp damage with iron shield.
Rolling is safier when you get the pattern ;)

cheese it:
dig under one of the unbreakable trees; raise the ground (you will actually be inside the tree at this point)
drop a workbench
use stagbreaker to attack through the tree and hammer him to death!
only thing that will hit you will be poison cloud...if he uses it; which he often wont at such close quarters; but if you stock up on poison potions that wont be an issue.