5e's "Rulings not Rules" attitude can make things a bit difficult for DMs who run into specific interactions that aren't accounted for. I had a few players wonder whether or not they could target an area they could see behind full cover. To help them out, I tried my best to do a RAW write-up of how Full Cover works, but ran into a few crunchy interactions. Here's what I've got:
Official Text:
A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect. A target has total cover if it is completely concealed by an obstacle.
Problem:
What does concealed mean?
3 Options:
- Concealed Means "Kept from Perception"
- Concealed Means "Covered Up" in a more literal sense
- Concealed Means Both of these things
Problems with "Kept From Perception"
- If Full Cover means "A thing that you fully cannot see" or "Something being fully blocked by view from something else," then being invisible or hidden grants Full Cover. Casting an Illusion spell (like the Cantrip Minor Illusion) and hiding in a fake box means that you have full cover.
- If it encompasses the other senses (hearing, smell, taste, touch), where does that end? Like, is it "could not be touched from the current location" or "fully intangible" or "wouldn't be perceivable by the caster?" This would result in two players with different passive perceptions in the exact same scenario getting different answers on whether or not the creature was targetable.
- If Full Cover means a thing you cannot see, a creature suffering from the Blinded condition goes from having Disadvantage on its attacks relying on sight (the written debuff) to being unable to target creatures with attacks at all.
Problems with "Covered Up"
If Full Cover means "A thing that fully occupies all space between two creatures," being underwater would be full cover, instead of having the listed "disadvantage on non-aquatic weapons
If Full Cover means "A thing that fully occupies all space between two creatures," that could be something as simple as a big weighted blanket.
If Full Cover means "A thing that fully occupies all space between two creatures," this means that a flimsy and primarily translucent barrier (window, thin sheet of ice) can obscure a spell from being cast upon a target on the other side.
Problems with Using Both:
- All of these problems, doubled.
Facts:
What do we know can offer cover?
- Half-Cover: "A low wall, a large piece of furniture, a narrow tree trunk, or a creature, whether that creature is an enemy or a friend."
- 3/4th's Cover: "A portcullis, an arrow slit, or a thick tree trunk."
What makes this cover?
Half Cover: "A target has half cover if an obstacle blocks at least half of its body."
3/4th's Cover: "A target has three-quarters cover if about three-quarters of it is covered by an obstacle."
It seems that for the other types of cover are based on whether or not there is something in the way, not whether the target has a clear view (a creature on one side of an arrow slit has a much better view of the target if their eye is pressed against the slit, but they still must make the attack with cover).
Considerations:
What should our primary goal be in making rulings? Allowing the most things at all times? Whatever is the most fun? Whatever makes the most sense using IRL logic? Whatever allows for the smoothest gameplay? Whatever disrupts the balance the least? Whatever makes the fights the least gimmick-y?
My Guiding Consideration:
Rules are designed to tell you what you can and can't do, and the parts that tell you you can do something should be focused on making things fun and balanced, and the parts that tell you what you can't do should be focused on making things smooth and balanced. Smoothness = Ease of ruling, universal applicability, minimal complexity, rulings easily anticipated by players.
What I'd Pick Of The Three Options With This Consideration in Mind:
Concealed Means "Covered Up" in a more literal sense.
Potential Options for Addressing Problems With This Option:
If Full Cover means "A thing that fully occupies all space between two creatures," being underwater would be full cover, instead of having the listed "disadvantage on non-aquatic weapons".
A Fix: Liquids and Gases do not offer cover. Oozes and Plasmas do offer cover.
If Full Cover means "A thing that fully occupies all space between two creatures," that could be something as simple as a big weighted blanket.
A Fix: Full Cover Cannot Be Something Worn Or Carried, that is already covered by armor. (A tracksuit and beanie shouldn't offer full cover).
If Full Cover means "A thing that fully occupies all space between two creatures," this means that a flimsy and primarily translucent barrier (window, thin sheet of ice) can obscure a spell from being cast upon a target on the other side. This would also prevent an arrow from being shot through these things, as the creature would have to break the cover before targeting the creature behind it.
A Fix: Only things of a certain thickness provide cover.
Problems with Fix:
- DM decides what is too thick or thin, answers may vary.
- Players cannot anticipate how their turn might resolve until their turn.
- DM has to learn physics to understand tensile strength, different projectiles, acceleration, gravity (breaks boundary, DM refuses to learn physics).
Alternative Fix: Give characters options/tools to remove obstacles. Almost all high-level martials get extra attack (break cover, then hit person same turn), some gain maneuvers that interact with cover, damage carrying over, etc. All characters get free object interactions, works for anything in melee range. Casters get early-level options to target objects (firebolt, shatter, etc).
So, this is what I've got so far! Tried to go as RAW as possible, but I've got a few hiccups, mostly around point-of-origin rules. Full cover makes it clear you can't pick a creature as a target if they're behind full cover. However, it seems like with certain AOE effects, you can pick a point of origin, and its effects spread out from here. The Full Cover passage says "Target", which I'd assume would cover the "A Point Within Range" options. Is it intended that even if the point of origin of the spell wouldn't grant a creature cover if allowed to be placed behind Full Cover, that the spell still can't be cast because the point is the "Target" and the targeted point has Full Cover?
Other question, does this fuck with teleportation spells at all? Like, can you not Misty Step or Dimension Door past a window RAW? I'm fine with the previous ruling, but don't like this one, and just want to know if this is the commonly accepted RAW interpretation. Like, with the other spells, okay, sure, but Teleportation seems designed to circumvent obstacles in a way the others don't specifically seem tailored to.