How do I defeat the goo?

Find a water section to fight in, this will prevent the acid from harming you and washes it away immediately! Other than that a good weapon and armor and you will get him!

Other small strategies: a scroll of terror to make him run and than throw some fire at him! with weapon recommend having a weapon that you have 1 strength higher than requirement, and aim to be level 5 before you meet him.

After playing a lot, here are some tips:

1. The Goo seems to be armored; prefer high-damage weapons to faster but low-damage ones.
2. The Goo heals 1 hp every turn in which it stands in water; prefer fighting it when it's on a dry surface.
3. The Goo's acid washed away instantly in water; so prefer fighting where you stand in water.
4. When the Goo "pumps itself up", it doesn't do anything for a few rounds, and then does a devastating attack. The attack has a range of 2 tiles, not just 1 like other melee attacks. Ways to break it:
   1. Leave the attack's range
   2. Become invisible
   3. Kill the Goo

So my main strategy is to place myself in water next to a dry place from which the Goo will attack, and when it pumps itself up either stay and hit it (if I have a good armor and HP to spare) or retreat to cancel the attack. Also, standard boss tricks (becoming invisible and shooting it, using poison / paralysis potions etc.) work well.

The easiest solution I've found is a combination of a few of the other techniques mentioned here. The door to Goo's lair is always 1 wide and usually has some water.

• Plant an earthroot seed in the patch of water nearest the door to get the armor buff and immediately wash off Goo's goo.
• Plant any damage over time (fire or poison) seed in the doorway. Standing on the seed won't trigger it.
• Throw something at Goo to get its attention and walk back to your earthroot
• As Goo approaches throw anything at it for a few hits.
• Tank Goo from your watery rooted stronghold.

This approach works with almost any standard armor and weapon combo for any class. With a warrior I never need a health potion with this strategy. Wizards are a little squishier but this can be overcome with a potion or two.