Thunder (rune)

Thunder was a type of giant rune that allowed the wielder of its inscribed object to call lightning down upon their foes.

Effects
The thunder rune had several limitations. Firstly, its effects could only manifest during a natural thunder or rainstorm. Secondly, it could not be targeted against creatures inaccessible to the sky, such as ones indoors or underground.

When the inscribed hammer was struck against the ground during an appropriate storm it would conjure a lightning bolt, one for each thunder rune, to strike against whoever the wielder desired. These bolts were equivalent to ones cast by a level-7 wizard, though casters who extensively studied this rune a second and third time could make the lightning bolts as powerful as ones cast by level-9 and 11 wizards respectively.

Components
Like most giant runes, it required no material components to cast, though the caster needed to know the giant rune strength. The process of shaping this rune could take anywhere from one to three days and it needed to be inscribed upon a hammer. Up to three of these could be shaped on to a single hammer.