Horus Rising pg. 232

Giant forks of lightning, savage and yellow-white phosphorescent, were searing down into the open space, explosively scorching the earth. Though each fork only existed for a nanosecond, they seemed solid and real, like fundamental, physical structures, like up turned, thorny trees. Three Astartes, including Lucius, were struck. Secure in their Mark IV plate, they shrugged off the massive,detonating impacts and laughed as aftershock electrical blooms crackled like garlands of blue wire around their armour for a few seconds.

The storm above grew still more ferocious. Five more men were struck. One of them, Ulzoras, was actually knocked off his feet. They saw fused, glassy craters in the ground where lighting had earthed with the force of penetrator missiles.