[RPG] Can you use a weapon & magic at once

dnd-5espellstwo-weapon-fighting

Is it possible to attack with a light one-handed weapon and then cast a spell in the other hand à la two-weapon fighting (just with casting a spell instead of using another melee weapon)? From my understanding, casting a spell isn't the same kind of Action as Attacking, but since many Somatic-component spells only need one free hand to work I don't see why it wouldn't apply the same way as TWF. It seems rather silly that one could hold a light weapon in one hand and cast a spell in one hand but not do them both at once.

If not I'll likely just ask my DM to see if he'd allow it and put his own penalties on it if need be but I wanted to make sure there was no official ruling first. I'm very new to D&D and can't seem to find an answer to this specifically, so bear with my ignorance please. Thanks.

Best Answer

Yes, but only in specific cases.

First, you can use your bonus action to cast a spell and your action to take the attack action. Only a handful of spells have a casting time of a bonus action, though a sorcerer can use the Quicken Spell metamagic to reduce a spell's casting time to 1 bonus action, at the cost of sorcery points.

Second, A Valor Bard can cast a spell with a casting time of one action and use their bonus action to attack--their level 14 class feature states (PHB 55):

At 14th level, you have mastered the art of weaving spellcasting and weapon use into a single harmonious act. When you use your action to cast a bard spell, you can make one weapon attack as a bonus action.

Third, a 2nd level fighter is able to use action surges, which gives you an extra action (that you can use to cast a spell or attack)

Finally, an Eldritch Knight can cast a spell and make a single attack in a round at various levels:

Beginning at 7th level, when you use your action to cast a cantrip, you can make one weapon attack as a bonus action.

Starting at 18th level, when you use your action to cast a spell, you can make one weapon attack as a bonus action.

Allowing this more generally might make you overpowered.

D&D 5e's action economy and balance revolves around managing a character's action and bonus action. The DMG warns: (DMG 263)

Rules and game elements that override the rules for concentration, reactions, bonus actions, and magic item attunement can seriously unbalance or overcomplicate your game.

Allowing a character to effectively have a second action almost doubles that character's power. The features described above either have pretty tight restrictions that reduce the potential damage output or very high level requirements. If you or your DM want to homebrew a similar feature, you should take some care to balance it.

If you want to think about it in in-game terms, consider that casting a spell requires focus (concentration, one might say), skill, and effort to cast. Attacking with a second weapon might be an extra swipe or two with your off-hand, but committing to a spell is a much bigger deal and takes much longer. A single turn is only 6 seconds, after all!