A lightning rod, yes.

He touched their barometer, a holy item, as it heralded approaching lightning storms.

As they approached the rod from all directions, surrounding him, the Hemulen climbed up the pole in fear.

He would have been fine though, Hattifatteners are only dangerous during storms, when they've been struck, as they carry the energy of the lightning.

Outside of that, they're quite harmless, though he did upset them by messing with their stuff.