Basic perception

[Dmdork]

Let's talk about perceiving/targeting/attacking creatures that are invisible or in heavily obscured/total darkness, or creatures that are blind and trying to target other creatures. In all of those instances you know where your target is (unless they stealth) and can still cast spells at it (unless spell says you have to 'see') and there's no perception check needed. Right? RAW, or am I off a bit on this logic?

[BurgerBeast]

There is debate about this. I would personally say no, but there are many who would say yes.

[Quoz]

I might not be able to hit you with an arrow, but I could fill your corner of the room with a fireball.

Like most things, context is important. If they are standing and trading blows with you or someone else, enough to get a good idea of their rough position, most spells that don't require sight should be fine. Attacks will probably be at disadvantage.

If you fighting something using hit and run or ranged attacks where you can't figure out where they are, I would probably require perception vs stealth. Taking an action to perceive, either for yourself or as part of the help action to spot for an ally, would improve your chances. Even on a near miss, I would probably help narrow it down enough to hit with an AoE spell.

[Dmdork]

Well, sounds like you're just takin it as it comes and makin your own calls, as a DM should. That's what I'm doing now. I was just wondering if theres anything definitive I missed that would lend weight or contradict my interpretation of the rules.

[Blood of Gaea]

If they don't have a sense to get around it, I would make them roll a perception check. The humanoid races rely on sight primarily, so detecting someone through other sense requires effort.

[Tanarii]

In all of those instances you know where your target is (unless they stealth) A DM can always set a fixed DC and require a check to do something that they judge isn't automatically successful or an automatic failure. That may include a perception check to perceive a creature against a fixed DC. Such as a creature you have difficulty perceiving the exact location. Or even distinguishing creatures from one another, for that matter.

Examples:
- perceiving by sound the exact location of an unseen target 100 ft away that you can't hear clearly over the sounds of the fighting going on right next to you.
- perceiving by sound the exact location of an unseen creature 15 ft away in a battle in a very loud forge or marketplace.
- distinguishing particular creature 500 ft away from you in the middle of a melee of enemies and allies through heavy rain or mist.

That doesn't mean a DM should or will do that. Just that setting DCs for things the DM thinks have a chance of success or failure is part of what we do. And in my AL experience, they won't. They'll just have you auto-detect any not-hiding creature.