D&D General I hate five-foot passages!

[Maxperson]

Five-foot reach. The slaad must be adjacent to strike.

Cover is a +2 or +5 bonus, and with the right feat, no cover at all (I think the Sharpshooter feat is very, very poorly created).
For melee purposes, it's a +2 bonus to AC.

The rogue is rolling with advantage and +9 to hit against a AC 21 with superior cover. That's not enough to protect the slaad very well.

Just to illustrate, the rogue can see about half the Slaad from his sniping position here. It might be a little less, but that's still a LOT of the slaad he can see. That's half cover, or a +2 AC bonus. (The slaad needs three quarters blocked to get the +5 bonus to AC).

View attachment 348520

If the Slaad can squeeze into the hallway, it can squeeze into a corner to avoid being shot with an arrow and force the party to enter the room to deal with them.

 

[Rabulias]

Just to illustrate, the rogue can see about half the Slaad from his sniping position here. It might be a little less, but that's still a LOT of the slaad he can see. That's half cover, or a +2 AC bonus. (The slaad needs three quarters blocked to get the +5 bonus to AC).

Reading the door as a full 5 feet wide opening, I would say the slaad has no cover to the rogue, as the rogue has full view of one of the slaad's squares. See the DMG quote and illustration below. If the door is only as wide as shown on the map, then yes, half cover would apply.

To determine whether a target has cover against an attack or other effect on a grid, choose a corner of the attacker’s space or the point of origin of an area of effect. Then trace imaginary lines from that corner to every corner of any one square the target occupies. If one or two of those lines are blocked by an obstacle (including another creature), the target has half cover.

 

[Maxperson]

Reading the door as a full 5 feet wide opening, I would say the slaad has no cover to the rogue, as the rogue has full view of one of the slaad's squares. See the DMG quote and illustration below. If the door is only as wide as shown on the map, then yes, half cover would apply.

View attachment 348647

The slaad can squeeze into the corner like it squeezes into a 5 foot hallway. That eliminates the seen square.

 

[tetrasodium]

The slaad can squeeze into the corner like it squeezes into a 5 foot hallway. That eliminates the seen square.

Spoiler

Squeezing into a Smaller Space​

A creature can squeeze through a space that is large enough for a creature one size smaller than it. Thus, a Large creature can squeeze through a passage that's only 5 feet wide. While squeezing through a space, a creature must spend 1 extra foot for every foot it moves there, and it has disadvantage on attack rolls and Dexterity saving throws. Attack rolls against the creature have advantage while it's in the smaller space.

Combat

D&D Beyond - Dungeons & Dragons Fifth Edition Tools, Rules, Races, Classes, Items, Spells, Monsters, and More

www.dndbeyond.com

5e broke it badly in every way. The PCs are not at all constrained and the monster may as well die by fiat to save everyone the boredom of clowncar physics where PCs move through each other to attack then move back to stay safe. Id say that the PCs could get advantage by flanking from both sides but they get that automatically from squeezing

 

[Maxperson]

Spoiler

Squeezing into a Smaller Space​

A creature can squeeze through a space that is large enough for a creature one size smaller than it. Thus, a Large creature can squeeze through a passage that's only 5 feet wide. While squeezing through a space, a creature must spend 1 extra foot for every foot it moves there, and it has disadvantage on attack rolls and Dexterity saving throws. Attack rolls against the creature have advantage while it's in the smaller space.

Combat

D&D Beyond - Dungeons & Dragons Fifth Edition Tools, Rules, Races, Classes, Items, Spells, Monsters, and More

www.dndbeyond.com

5e broke it badly in every way. The PCs are not at all constrained and the monster may as well die by fiat to save everyone the boredom of clowncar physics where PCs move through each other to attack then move back to stay safe. Id say that the PCs could get advantage by flanking from both sides but they get that automatically from squeezing

If they go into the room it would trigger the readied actions of the slaadi. Popping in and out is likely a bad idea or even if in the PCs favor still, certainly much less so that the slaadi going into the hallway.

 

[tetrasodium]

If they go into the room it would trigger the readied actions of the slaadi. Popping in and out is likely a bad idea or even if in the PCs favor still, certainly much less so that the slaadi going into the hallway.

They don't actually need to go in. Nearly every class can snipe it from the door & move awayby walking through one of their allies. This has been covered

Spoiler

Moving Around Other Creatures​

You can move through a nonhostile creature's space. In contrast, you can move through a hostile creature's space only if the creature is at least two sizes larger or smaller than you. Remember that another creature's space is difficult terrain for you.

Whether a creature is a friend or an enemy, you can't willingly end your move in its space.

If you leave a hostile creature's reach during your move, you provoke an opportunity attack, as explained later in the section.

Combat

D&D Beyond - Dungeons & Dragons Fifth Edition Tools, Rules, Races, Classes, Items, Spells, Monsters, and More

www.dndbeyond.com

Your readied action doesn't work too well either

Spoiler

Sometimes you want to get the jump on a foe or wait for a particular circumstance before you act. To do so, you can take the Ready action on your turn, which lets you act using your reaction before the start of your next turn.

First, you decide what perceivable circumstance will trigger your reaction. Then, you choose the action you will take in response to that trigger, or you choose to move up to your speed in response to it. Examples include "If the cultist steps on the trapdoor, I'll pull the lever that opens it," and "If the goblin steps next to me, I move away."

When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger. Remember that you can take only one reaction per round.

When you ready a spell, you cast it as normal but hold its energy, which you release with your reaction when the trigger occurs. To be readied, a spell must have a casting time of 1 action, and holding onto the spell's magic requires concentration. If your concentration is broken, the spell dissipates without taking effect. For example, if you are concentrating on the web spell and ready magic missile, your web spell ends, and if you take damage before you release magic missile with your reaction, your concentration might be broken.

Combat

D&D Beyond - Dungeons & Dragons Fifth Edition Tools, Rules, Races, Classes, Items, Spells, Monsters, and More

www.dndbeyond.com

Of course it does not matter even if the Slaad does that because the PCs can just send in someone else first if the Slaad manages to actually injure someone meaningfully. Sure the slaad could ready an action to only attack Bob, but that kinda tactical choice only works until the party starts throwing in things like shocking grasp or any number of other reaction blocking abilities into their default combat rotation

 

[Weiley31]

It's hard to use a 10-foot pole properly in such a situation.

 

[Maxperson]

They don't actually need to go in. Nearly every class can snipe it from the door & move awayby walking through one of their allies. This has been covered

They DO have to go in since the slaadi are squeezing into the corner of the room and can no longer be seen since they aren't taking up a large size creature space. If they can squeeze into a 5 foot corridor, they can squeeze into those corners.

Your readied action doesn't work too well either

It works just fine. "When a PC moves into the doorway I will X." You interrupt the PCs turn when it gets into the doorway and the slaadi can attack the PC before the PC gets to attack.

 

[Hussar]

But then the pcs move in with no opportunity attack and move to keep the salad squeezing, which is pretty much a death sentence. That’s a really bad tactic for the slaad.

 

[Maxperson]

But then the pcs move in with no opportunity attack and move to keep the salad squeezing, which is pretty much a death sentence. That’s a really bad tactic for the slaad.

They couldn't use an opportunity attack if they did get one. They readied an action which includes movement and attack, so the squeezing has ended and the person entering the room is attacked with the reaction.