When first found in the world, these robotic husks will be covered with moss and foilage, presumably because they have been dormant for quite some time. They are unassuming heaps of overgrown robot parts that will come to life and attack the player or anything nearby when mined with a Pickaxe. They can also be stirred to life with lightning, where they will be activated for longer period of time than if they were mined. During the Aporkalypse, the Iron Hulk will remain activated constantly.
There are four different parts to be found: a head, a torso, a leg, or an arm. The arm and torso are by far the most devastating ones, as they will shoot a giant laser beam that procs small explosions in a straight line, which can cause immense damage, and if unarmored, can instantly kill the player. These lazers will also light structures, plants, and mobs on fire. The head and the leg will perform a smash attack, where they will leap at their target and smash down, doing a small AOE attack that also starts fires, and can proc multiple times if an entity is closer to the center of the attack.
The player can, however, farm Iron Ore by mining them repeatedly. Since their attack AI targets the players location only when they start their attack animation, the player can ocasionally hit them when they're still active.
It is recommended to mine the ribs. Although they do the most damage, their attacks are the easiest to dodge. The ribs also have a longer pause between attacks, allowing the player to mine it for longer without dodging attacks.
The biome Iron Hulks are found in are often next to Thunderbirds. This can cause the Iron Hulks to be struck by lightning, awakening them and often wreaking havoc to nearby mobs.
Thunderbirds also don't run away from hulks, thus when killed by one are set on fire and won't drop Thunder Feathers.
The ribs and arm pieces can attack with their lasers in melee range, even if they just attacked at range. Be wary when mining these pieces while they're activated.