From DivNull RPG
An air-aspected Casket of Firedust Conversion inlaid with deep blue jade in swirling patterns resembling clouds, that turns firedust into skydust.
A firewand with skydust fires a streak of lightning. This inflicts eight dice of lethal damage and ignores half the target's armour's soak, rounded down. This applies even to magical armour. Extra successes on the attack roll do not grant extra damage dice on this attack.
Committed skydust creates a streak of lightning, which, as always, ignores half the target's armour's soak. If the target fails to dodge, then the lightning hits them for 12 dice of lethal damage, then leaps on from them to hit two more targets -- the two nearest people to the first target.
The original successes from the first attack roll against the first target are halved (rounded up -- these dice will continue to be halved for later attacks until they get down to 1; there are no further attacks after that) and applied to the attacks against these next two targets; the new targets may dodge the branching lightning, their dodge rolls opposing the halved successes. The damage on these two attacks is 6 dice of lethal damage.
If these two targets are hit, then the lightning branches yet again and goes on to hit two more targets from each of them. The successes on the attack are halved again for the purposes of dodging, and the attacks do 3 dice of lethal damage.
The lightning keeps branching and halving the attack's successes and the damage until it either runs out of attack successes or runs out of damage successes (it runs out of damage successes after it makes an attack that does 1 die of lethal damage). At this point, it grounds itself.
Whenever the lightning misses a target, it does not branch, instead grounding itself immediately.
Extra successes on the attack rolls do not grant extra damage dice on these attacks. The person who fired the firewand is not immune to this effect; should he happen to be the closest person (or the second closest) to anyone hit by one of the lightning-branches, and the lightning branches after that person, then one of the lightning branches will go after him.
Example: Ledaal Anything, the Air Aspect, is firing a firewand with skydust. She fires her firewand, using her 5 Dexterity and 5 Archery, at a nobody. Anything gets 10 successes on her attack roll (she did really well). The nobody has 3 dice to dodge, and gets 1 success -- not enough. Luckily for the nobody, he has armour that grants him 4 lethal soak.
The extra successes on Anything's attack roll did not count towards damage, so for her damage against Mr. Nobody, she rolls 12 dice minus Mr. Nobody's armour soak of 4, divided by 2 for the electricity effect. So Anything rolls 10 dice of damage against the nobody.
Now the lightning branches off from the nobody and attacks two more nobodies with 5 attack successes each (Anything's original attack successes, divided by 2). The new nobodies each get 1 success on their respective dodge rolls -- still not enough. However, Anything rolls only 6 dice of lethal damage against them, minus their halved armour's soak of 2, for 4 total damage dice.
Now the lightning branches off again from the second two nobodies and attacks four new nobodies with a total attack successes of 3 each. Two of these nobodies miraculously manage to dodge, so two of the branches of lightning ground themselves harmlessly; however, two of the nobodies are hit. They have the same lethal soak as the first three nobodies, so they take 3 dice of damage, minus 2 -- 1 die of lethal damage.
The lightning keeps branching off from each person it hits until either all of the branched lightnings have been dodged, or the attack successes or damage dice have been reduced to 0.