In this question, I asked about whether a character could willingly not use their shield or Dex bonus on certain attacks due to wanting to be hit. This raises the greater question-
Can someone decide to be hit?
The question was answered here, but it is for 4e, and I am asking about 5e. This question is assuming that a hostile enemy is making an attack roll against a PC, and the PC in question wants to be hit by the attack.
With a character making little to no effort to defend themselves, you create a circumstance where the attacker has advantage.
Sometimes an ... attack roll ... is modified by special situations called advantage and disadvantage. Advantage reflects the positive circumstances surrounding a d20 roll, while disadvantage reflects the opposite. (Basic Rules, p. 4)
Advantage means two d20 rolls for the attacker; use the best score.
The DM can also decide that circumstances influence a roll in one direction or the other and grant advantage or impose disadvantage as a result. (Basic Rules, p. 57)
Simply advising the DM that you are doing nothing to defend yourself may cause the DM to give the attacker advantage. While there isn't an action called "anti dodge" not defending yourself is the opposite of the dodge1 action, which imposes disadvantage on the attack (mechanically). You can set up a signal with your DM -- "I am going to anti-dodge this round" -- to help speed up play. (Work with your DM to fit this to your table).
If there is a melee attack being made upon you, falling down creates the prone condition. Your character being prone will provide the attacker with advantage on the attack (Appendix A; Conditions; Prone) within 5' of the prone character. (An exception to this is a lance attack which has disadvantage on attacks within 5')
The attacking enemy can still screw up on a given attack, in a general sense; rolling a 1 for a melee or ranged attack is always a miss2. Even in a case where the roll is made with advantage, which depending on AC will accrue a to-hit bonus of +4 or +5 (in terms of probability), the attacker can screw up and not make an effective hit.
A complete miss is less likely with advantage on an attack, but it is still possible.
Paralyzed
• Attack rolls against the creature have advantage.
• Any attack that hits the creature is a critical hit if the attacker is within 5 feet of the creature.
The character can apply some Crawler Mucus in order to get paralyzed.
Crawler Mucus (Contact).
A creature subjected to this poison must succeed on a DC 13 Constitution saving throw or be poisoned for 1 minute. The poisoned creature is paralyzed. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. (SRD V5.1 p. 204, DMG ref later)
See Tom's answer for why rolling the dice need not be necessary. Discuss that with your DM.
1Dodge
When you take the Dodge action, you focus entirely on avoiding attacks. Until the start of your next turn, any attack roll made against you has disadvantage if you can see the attacker, and you make Dexterity saving throws with advantage. You lose this benefit if you are incapacitated (as explained in appendix A) or if your speed drops to 0. (Basic Rules, p. 72)
2Rolling 1 or 20
If the d20 roll for an attack is a 20, the attack hits regardless of any modifiers or the target’s AC. This is called a critical hit, which is explained later in this chapter. If the d20 roll for an attack is a 1, the attack misses regardless of any modifiers or the target’s AC. (Basic Rules, > p. 73)
There are not infinite spell slots. Based on the referenced GiTP thread, and presuming not-a-five-minute-adventuring day: if the character inviting this attack has a shield, but wants to be hit to exploit Armor of Agathys, then they are better off using their action that turn to doff (remove) the shield (it takes on action to do so) which removes its +2 from the armor class.
Doff. This is the time it takes to take off armor. If you have help, reduce this time by half.
Category / Don / Doff Shield / 1 action / 1 action (Basic Rules p. 45)
The dexterity element of armor class isn't as easily discarded, but with the benefit from advantage being about +4 to +5, the advantage should at least take care of the dexterity bonus to armor class. (Depending upon the attackee's dexterity score).
D&D 5e includes a general principle that dice are only rolled if the result of an action is uncertain. The DM is not required to call for a die roll at all, even for a hit, if the circumstances are right for that. (This is particularly true in "Theater of the Mind" style games). When discussing this with your DM, you can probably get agreement on this since this approach draws from the game's basic structure and intended play style.
If I want to be hit, and the monster wants to hit me, I don't see which reasonable circumstances could result in a miss. Therefore, no dice need to be rolled. That ruling is consistent with How the Game is Played as described in the rules1.
Caveat 1: We are talking about melee combat. In ranged combat, you can miss the broad side of a barn if you are somewhat away. At melee distance, unless you are holding a sword for the first time in your life, you won't miss it.
Caveat 2: To retain the risk of a critical hit, the DM can roll the dice to see if a 20 crops up but not worry about any other result.
1Reference in the Basic Rules, page 3:
How to Play
1. The DM describes the environment.
2. The players describe what they want to do. {format and italics added}Sometimes, resolving a task is easy. If an adventurer wants to walk across a room and open a door, the DM might just say that the door opens and describe what lies beyond. But the door might be locked, the floor might hide a deadly trap, or some other circumstance might make it challenging for an adventurer to complete a task. In those cases, the DM decides what happens, often relying on the roll of a die to determine the results of an action.
3. The DM narrates the results of the adventurers’ actions. Describing the results often leads to another decision point, which brings the flow of the game right back to step 1... play is fluid and flexible, adapting to the circumstances of the adventure.
The rules on attack rolls made against player characters in combat are clear:
When you make an attack, your attack roll determines whether the attack hits or misses. To make an attack roll, roll a d20 and add the appropriate modifiers. If the total of the roll plus modifiers equals or exceeds the target's Armor Class, the attack hits. The AC of a character is determined at character creation, whereas the AC of a monster is in its stat block.
There is no standard rule which allows you to voluntarily take a hit. You can increase the likelihood of being hit, by taking actions which give attackers Advantage, or provoking opportunity attacks, or wearing less armor, or temporarily removing or disabling items that benefit armor class.
However, DMs can house-rule situations like this, so your particular DM might allow it. Jeremy Crawford says that he might allow the similar situation of deliberately failing a saving throw. D&D 5th edition's rules don't cover every possible scenario, and many uncommon circumstances like trying to deliberately take a hit are intentionally left to the DM.
I'd guess no, since even the best of intentions can't guarantee that a poorly skilled attacker could land a blow. Take a game of catch, for example. As the recipient, you are trying to catch the ball, and the thrower is trying to throw it to you, and yet even with both parties cooperating, it is possible for the catcher to miss.
However, I would certainly think that the defender could voluntarily provide the attacker advantage by leaning in to the attack.
That is an interesting question. When reading through the rules, I haven't come across anything that specifies that one can or cannot be auto-hit.
I believe that this would still be a DM specific call. Now, in the question that you are referencing, there is the desire for a PC to be hit as they have Armor of Agathys on themselves.
As a DM, I would lean towards allowing it to happen with a caveat. The rules for being hit while unconscious apply. It's an automatic critical hit against the PC. That would balance out the Armor of Agathys and make it a potential concern for the player, while they could use it, it would be a balancing act.
I would rule it one of two ways, and let the player decide.
The attacker gets advantage on the roll as you purposefully leave yourself open to the attack. Leaving yourself a little more open to an attack doesn't meant the attacker notices or is able to hit you the way you want. The attack may still miss.
You purposefully leave yourself wide open to an attack. There is no attack roll made; the attack hits, but it is treated as an automatic critical hit. If you definitely want to get hit, the attacker is going to take that opportunity to deal some serious damage.
