What kinds of spells can be cast while blindfolded?

Question

The Player Character (a Sorcerer/Warlock) is talking to an enemy while being blindfolded. Therefore he cannot see the enemy, but obviously hear him. Which spells can he cast?

1. Ranged Spells that require an attack roll

   For example Scorching Ray. I assume he would have disadvantage, because he is effectively blinded, but he could try.

2. Spells on himself

   For example Mage Armor. I see no problem here.

3. Spells that require touch

   For example Vampiric Touch. If he's already touching the enemy, he could cast it. Otherwise he would have to make a succesful melee attack, again with disadvantage.

4. Ranged Spells that do not require an attack roll

   For example Sleep. I'm not sure on this one. Can he just cast it?

5. Magic Missile

   I would assume that he cannot cast Magic Missile at all, as it requires him to see the target. Or can he just shoot the missiles blindly and hope to hit something?

Answer 1

Overall, there are three main mechanics for you to consider/understand.

First: Does the spell require "a target you can see". That target can be a person, place, or thing. If the answer is yes, then that spell is not an option to cast.

Second: If Question 1 is "no", and if the spell requires a spell attack roll, then you do so at disadvantage. This is a function of the Blinded condition (which, you functionally are if blindfolded).

PHB, 290 The creature's attack rolls have disadvantage

Third: If Question 1 is "no", and if the spell doesn't require a spell attack roll (automatic or saving throw related), then you may cast as normal.

To answer your specific spell questions:

1. Yes, you are correct. This would be done at disadvantage

2. Works as normal. No requirement for "seeing the target" and no attack roll.

3. See notes above, for Vampiric Touch it doesn't require you to see the target (which is yourself). However, the spell still requires a melee spell attack which will be done at disadvantage per the Blinded condition.

4. Generally, see my requirements above, but for Sleep it would work as normal. No requirements for choosing something "you can see" and no spell attack roll.

5. Requires a "target you can see". You can not cast this spell while blinded.

Answer 2

All the blinded condition does is prevent you from seeing, grant attacks against you advantage, and your attacks disadvantage. It does not directly do anything to your spell casting ability, but spells that require attack rolls or for you to see your target will be affected.

1. If the spell doesn't require a target you can see the attack will be made with disadvantage. If it requires a target you can see you can't cast it.
2. Unchanged
3. If it requires an attack roll that will be with disadvantage.
4. If the spell requires you to see your target you can't cast it, otherwise it is unaffected.
5. MM requires you to see the target so it will not work.