Firearms were originally designed by Harold, and balanced by Aidan.
Firearms are not unlike our own world's, but powered by magic (a fuel cell) rather than explosives. They are two-handed martial ranged weapons whose base damage is 1d12 and scale with Dexterity, and can store 100 bullets of ammunition. (Alternatively, light guns are one-handed, doing 1d6 damage but scaling with Dexterity.) The fuel cell has 10 charges. Any class that would have proficiency with bows also has proficiency with guns, but you could also just ask me for proficiency and I might give it to you. Their range is 100/400.
Each fuel cell assigns the gun an element. Aside from determining their damage type, elements have the following effects:
- Fire - Combustion-powered rifle (similar to a real-world gun). +2 to damage.
- Lightning - Railgun. +2 to hit.
- Earth - Handcannon. Target must make a Con save (DC = Spellcast DC of charging caster) vs stagger.
- Thunder - Sonic gun. Target must make a Con save (DC = Spellcast DC of charging caster) vs deafen.
- Ice - Frost ray. Target must make a Con save (DC = Spellcast DC of charging caster) vs losing 10' movement speed for a turn.
Recharging the fuel cell requires a caster to use any cantrip, which restores 10 charges. This takes a main action. I'll assume that you recharge outside of combat, so that ammo is only really a problem if you split the party or if combat lasts for more than 10 turns.
Moreover, for certain higher-end guns, a caster can use a higher level spell slot to hypercharge the gun, and for the next three shots, the gun will have the following added effect, assuming that the caster used spell slot N:
- Fire - Exploding shot. Extra Nd12 damage.
- Lightning - Chain spark. If there is an enemy within 30' of the target, the bullet chains to them, damaging them as well. This repeats up to N times.
- Earth - Earthshock. Target is stunned until the end of its turn in N rounds.
- Thunder - Gale force. Does splash damage in a N * 10' radius around the target.
- Ice - Hypothermia. If target has already lost movement speed, must make a Con save vs incapacitation.
The following elements are much harder to come by, and can't be bought at will:
- Psychic - Mind blast. Ineffective against enemies with <4 Intelligence, but target must make a Wis save (DC = Spellcast DC of charging caster) vs short-term madness.
- Hypercharged Psychic - Mind blown. If the target is already suffering the effects of madness or rolls a natural 1 on their saving throw, part of their brain is destroyed, doing an additional 2Nd12 damage -- and if it is mortal damage, their head explodes.
- Radiant - Purifying light. +4 damage to anyone of an opposing alignment to the wielder (a true neutral wielder instead does +3 damage to anyone who isn't true neutral).
- Hypercharged Radiant - Holy hand grenade. For each sin the target has committed without confession "recently" does an additional +2 damage, up to +2N. Instantly fatal to rabbits and similar vermin.
- Necrotic - Lifeless ray. Up to 1d8 of the damage dealt heals the wielder.
- Hypercharged Necrotic - Necromantic virus. If target dies in the next N turns (stacks, so shooting him and then shooting him again sets this to 2N - 1 turns) he will rise as a zombie under the wielder's control, but returns to ash in 1d6 hours.
- Acid - Acid blaster. Corrodes target's armor and skin. If target fails a Dex save, their armor loses 1 AC of potency. If it drops to 10, the armor is destroyed;.
- Hypercharged Acid - Hydrochloric solvency. If target has no armor to speak of upon failing Dex save, their epidermis is corrupted, and they lose 1d4 CON for the remainder of the combat -- this affects their max HP. A drop of 5 CON is equivalent to a permanent loss of 1 CON.
Also, I reserve the right to start playing sinful Only my Railgun remixes in roll20 when people fire a railgun.