[Radiance] Weapon - Thunderstrike

Early aspects of railbow technology can be traced back to this innovative Corespark assault tool. The pro: an unstable energy-inefficient power core in the weapon launches projectiles from this crossbow at deadly speeds. The con: there's an unstable energy-inefficient power core in the weapon.

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Thunderstrike
Weapon (heavy crossbow), rare (requires attunement)

You have a +1 bonus to attack and damage rolls made with this weapon.

Chargelight Rail. This weapon can hold a maximum of 3 charges. While the weapon has at least 1 charge, it sheds dim light in a radius equal to 5 times the number of charges it has. Additionally, ammunition launched from it glow with dim light during flight and deal extra lightning damage to targets they hit. The extra damage equals the number of charges the weapon has.

Unstable Core. The weapon gains 1 charge each time you miss an attack made with it, its energy crackling unexpended. Whenever this weapon would gain a charge while it already has maximum possible charges, the energy immediately overflows. Roll a d6 and consult the Lightning Discharge table to determine what happens; then roll a d4 and consult the Charge Depletion table to determine how charges are expended. You can use an action to crank a release valve on the weapon to deplete all of its charges.

Lightning Discharge
d6 / Effect

• 6 - A blast of energy erupts from the weapon, producing the effects of a lightning bolt spell as if you had cast it (save DC 15). Instead of its normal damage, this effect deals 2d6 lightning damage for each charge the weapon has. The spaces that this effect's line passes through sparkle with residual energy and are filled with dim light for 1 minute.
• 5 - Excess energy vents from the weapon into your ammunition. The first attack roll you make with this weapon before the end of your next turn deals an extra 1d10 lightning damage.
• 3-4 - Sparks burst forth from the weapon in a 10-foot radius sphere centered on it. The sphere is filled with dim light for the next 1 minute, and creatures in this dim light cannot benefit from invisibility.
• 1-2 - An explosive shock erupts from the weapon. The weapon produces the effect of a thunderwave spell whose area is centered on itself (save DC 15). Instead of its normal damage, this effect deals 1d8 thunder damage for each charge the weapon has. You are also subjected to the spell’s effect. The effect’s area glows with dim light until the start of your next turn.

Charge Depletion
d4 / Effect

• 4 - The weapon loses 1 charge.
• 3 - The weapon loses all of its charges.
• 2 - The weapon overheats. It loses all of its charges and can't gain charges for the next 10 minutes.
• 1 - The weapon undergoes a contained meltdown. It loses all of its charges and can't gain charges for the next 1d4 hours.

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Uncommon Variant. The uncommon version of the weapon does not grant a static bonus to attack and damage made with it (it still benefits from the extra damage detailed in its Chargelight Rail property). The DC of its Lightning Discharge effects are 13.

Very Rare Variant. The very rare version of the weapon grants a +2 bonus to attack and damage rolls made with it, and has a maximum of 4 charges instead of 3. The DC of its Lightning Discharge effects are 17.

Legendary Variant. The legendary version of the weapon grants a +3 bonus to attack and damage rolls made with it, and has a maximum of 4 charges instead of 3. The DC of its Lightning Discharge effects are 18.

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DESIGN COMMENTARY

One of my favorites for sure, but a pain to balance. The weapon's conceit is pushing it toward more powerful, while also taking on risks when it reaches a certain threshold.

The weapon grants a basic +1 bonus to attack and damage to encourage its continued use. Each time you miss it starts to deal more damage, making it stronger while you use it. When the charges overflow, something (mostly bad) happens: a 1/6 chance of dealing great damage, 1/6 chance of dealing ~5 extra damage, a 2/3 of producing a mainly neutral effect, and a 1/3 chance of dealing damage to yourself. Granted the last option could be utilized to deal damage in a radius around you, but it's not particularly synergistic on a ranged weapon wielded by someone who would want to maintain distance. After losing charges, there's a 1/4 chance of starting from scratch entirely, and a 1/2 chance of losing the charges for the rest of the fight (or more).

So that means while you might maximize the weapon's charges out of combat to enter battle with +3 damage, that places you on the brink of the deadly downsides, potentially ending the weapon's benefits for the rest of combat.

This was rather difficult to adjust because the numbers are so swingy. A smart character should be able to maximize its utility, either by remaining under the charge maximum or ensuring they can deal damage with the explosive shock by running into range at the last second.

Visually, the Corespark lumenguild is all about tinkering, using brass, cogs, wires, and blue energy for its design language. There's a slightly throughline from this weapon to the railbows of the Cosmos future, essentially removing the strings but keeping the arms, storing energy in cylindrical/disk shapes, and storing batteries in the buttstock (like the Helix Thunder). Tinker stuff is super complicated and takes forever to render, but looks good when complete. Metal was really difficult to render this time around because there were so many light sources, so this was a good exercise in the end.

The hand crank releases the charges' built-up energy; the three pairs of pylons simulate the "magnetic" "launch" rail of a future railbow, which also allows the lightning string to function like a regular crossbow string when launching objects (by striking each pylon in succession). The front lightning charges the bolts as they are launched, etc.