To build a Trebuchet, you will first need a Siege Foundation for it to stand on. After placing a Siege Foundation, you will need to place a Trebuchet Base on top of the Siege Foundation.

Craft a Siege Foundation and a Trebuchet Base in the crafting panel of a Carpenter's Bench.

Some objects, such as Trebuchets, require you to build them in multiple stages. While in mid-construction, a special upgrade-recipe can be found inside the trebuchet to complete the build.

Complete building the Trebuchet from the crafting panel of the Trebuchet.

Siege boulders function as ammunition for Trebuchets.

Craft a Siege Boulder in the crafting panel of a Trebuchet.

Once a Trebuchet has been loaded and some amount of counterweight added to it, you can aim it by turning it and increasing the angle of the Trebuchet Arm.

Firing the Trebuchet is a simple matter of pulling the right lever.

Crafting an Orb requires an Alchemist to be assigned to your Alchemist's Bench. Orb effects can be combined by throwing multiple orbs in the same location, and effects can also be cancelled by throwing a Water Orb at the same location.

Craft an Orb in the crafting panel of an Alchemy Bench.

Explosives come in various forms - from Explosive Jars to Traps.

Unlock Explosives from the Knowledge menu.

Traps can inflict damage or other effects on enemies.

Build a Trap using the Construction Hammer.