Goblin King

The Goblin King is one of the three bosses to spawn in the Dark Caves.

Behavior
Will summon goblins as soon as it notices the player.

Strategy
It is recommended to fight this boss somewhere where you have a lot of horizontal mobility.

Before you do anything, take out the 2 goblins before fighting the boss as they can mess up the fight for you which is bad because this boss does a lot of damage.

The Goblin King's charge attack is potentially his most dangerous attack, as that does a whopping 15 damage which is a lot for this early in the game. You can tell if he's about to do it if he raises his axe which makes a sound. You can avoid it by timing a jump, or jumping to a higher platform or behind him if you're not used to the timing between the axe raise and the charge. The downtime coming from this attack is a very good time to strike.

The Goblin King's grab attack is easily the most dangerous if there are any spikes near, as you could get thrown into spikes which is instant death without any spike protection gear. If the Goblin King withdraws his axe, he's about to do the grab attack. You can avoid it by timing a jump, or jumping to a higher platform. Jumping behind him works but if he's facing a nearby wall then run away before he bounces off the wall into you. The downtime coming from this attack is a good moment to attack the boss. Note that you can't free yourself by using frost nova if you're grabbed. If you're playing multiplayer, then you can free someone else who's being grabbed by using frost nova, and the player being grabbed will get stunned for a moment after he/she gets freed.

If the Goblin King lowers his axe slightly, then he does the jump attack. Stay away from the boss as attacking while the boss is doing this will almost guarantee you taking damage. The downtime is less compared to other attacks, so if you choose to attack during this downtime, then be wary of the Goblin King's next move.

Patience is key during this fight, as the Goblin King's attacks do high amounts of damage but they have a lot of downtime between them which is the only time when you should strike, and the goblins can be annoying as well if you decide not to kill them beforehand. If this boss spawns in a pit of spikes, then wait until his wall bounces or jumps destroy all of the spikes before facing the Goblin King.

Champion Variant
The champion variant has a red coloration, and is much more aggressive.

It attacks much faster with less downtime between each attack.

The boss will immediately summon new goblins at the latest opportunity if the old ones die.