The third tab of the Skill Window is reserved for abilities you acquire from steam machines.

Creating Steam Machines

A steam machine is any piece of socketed equipment that has a core machine inserted into it. Take a socketed armor or weapon and a core machine to any Steam Forge and select "Enhancement". Then, place your equipment in the middle slot and the core in the smaller slot on the right. When you confirm this action, your equipment will be transformed into a steam machine!

Core Skills

When you acquire a core machine, the ability that it gives you will be displayed on its tooltip description. This ability cannot be upgraded. If you want a higher-level skill, you need to find a higher-level core machine. Whenever you activate a core skill *, you will receive backlash damage. Also, after activation, the steam machine must cool down before you can un-equip it.

* Tip: You must have a steam machine equipped in order to have access to its core skill.