Ah, "Lightning Damage Compass" makes much more sense! Unlike the situation with physical damage, there’s actually a specific item in Path of Exile named the "Lightning Strike Compass."
The Lightning Strike Compass:
This is a unique belt available from the "Legion" encounter.
Its primary function is to manipulate the Legion encounter layout, specifically forcing the formation of two Lightning Strike Legionnaires who are guaranteed to drop a Lightning Strike skill gem when defeated.
While it doesn’t directly add or modify your own lightning damage, it’s highly valuable for acquiring the powerful Lightning Strike skill and building a character around it.
Other Options for Boosting Lightning Damage:
Unique Items: Numerous unique items offer lightning damage bonuses, like Voll’s Protector, Doryani’s Institute, and the Thunderfist gloves.
Skill Gems: Support gems like Increased Lightning Damage, Elemental Focus, and Added Lightning Damage can significantly boost your lightning output.
Passives: Various Ascendancy classes and passive skill tree areas offer lightning damage increases, like Elementalist’s Shaper of Storms ascendancy or the Lightning Walker cluster near Templar.
Flasks: Wise Oak flask is popular for hybrid life/mana builds while Atziri’s Flask can offer a temporary lightning damage boost.
Choosing the Right Method:
The best way to boost your lightning damage depends on your specific build and goals. Consider factors like your primary skill, ascendancy class, available uniques, and preferred playstyle.