No such rule exists.
There is simply no rule that says healing a creature with 0 hit points only counts as 1 hit point. The rules do say this:
The best way to save a creature with 0 hit points is to heal it.
A creature receives full healing from any healing spell while unconscious and at 0 hit points, and they immediately become conscious again:
Disguise Self does not end when you are incapacitated
According to the rules on spell duration in the Player's Handbook
A spell's duration is the length of time the spell persists. A duration can be expressed in rounds, minutes, hours, or even years. Some spells specify that their effects last until the spells are dispelled or destroyed.
There is no ...
You would not fail a death saving throw from taking damage while the ward is up.
The rules for Damage at 0 Hit Points say (PHB, pg. 197):
If you take any damage while you have 0 hit points, you suffer a death saving throw failure.
If you have your Arcane Ward (PHB, pg. 115) up while unconscious and are attacked, then:
Whenever you take damage, the ward ...
An unconscious creature is not affected.
The banshee's Wail action can only affect creatures "that can hear her":
All other creatures within 30 feet of her that can hear her must make a DC 13 Constitution saving throw.
However, most notably, part of the description of the unconscious condition states:
An unconscious creature is incapacitated, ...
Yes, the PC protected by Sentinel at Death's Door will take a single death saving throw failure
It's pretty straightforward if we look at all the pieces in sequence, and most of the citations are already in the question.
A creature at 0 hit points is, generally, subject to the Unconscious condition, which transforms any hit into a critical as long as the ...
There is no distinction between 0 hp and another value
Under Healing (PHB p. 197) there is no distinction between 0 hit points and any other amount. Neither is there any indication under Stabilizing a Creature (also p. 197) that healing would work differently than expected. Absent any specific mention of such a rule, we must conclude that 0 hit points are ...
This is a rule that your DM is recollecting from the 2nd Edition AD&D rules. From the 2E DMG (1992), Chapter 9: Combat, section on "Hovering on Death's Door (Optional Rule)" (that is, being permitted to live at 0 hp or below):
It bears highlighting that this is in the context of an optional rule to be extra-generous to player characters; the ...
Yes, with a ranged spell that does a melee attack
Arguably, you can knock them out at range with a Spiritual Weapon attack or the Clenched Fist from Bigby's Hand, or when attacking with spells like Animate Objects or Mordenkainen's Sword.
While your DM may not agree, we'll walk through the logic on this. Using as an example spiritual weapon (which reaches ...
No, there isn't. You are not missing anything.
The rules are very clear - you can only choose to deal a non-lethal blow with a melee attack.
The way I reason is that while you can easily control a melee attack, say, by hitting with the pommel of the sword, it is quite hard to control an arrow being thrown at an almost-dead character in order to not kill it. ...
They don't wear off
As you indicate, the duration of either potion is one hour, and there is no limitation should the affected creature become unconscious.
The general rules for magic items also make no mention of such a limitation. In fact, this is the only excerpt I could find addressing durations and potions:
Many items, such as potions, bypass the ...
What happens to their ward:
Does it drop to 0 hit points instead of the wizard? No, since it's not a damage dealing effect, the ward is not affected.
Does it disappear when the wizard drops to 0 hit points? No: there's nothing in its description that would make it do this. The wizard is at 0, but their ward is still as effective as it were if said wizard ...
It disappears 1 hour after it was created, or when it is reduced to 0 hit points.
You have emphasized the relevant rules text:
It disappears if it is reduced to 0 hit points or after 1 hour. You can dismiss it early as an action.
Nowhere is the cannon's existence tied to the Artificer's consciousness, so falling unconscious doesn't change anything about ...
Yes, this will cancel the auto-crit.
Specific rules take precedence over general ones, and Sentinel at Death's Door, being a class feature, is more specific than the rules for death-saving throws.
Sentinel at Death's Door specifies that it can be activated "when you or an ally that you can see within 30 feet of you suffers a critical hit" (emphasis ...
You are correct: the Eldritch Cannon stays around.
As stated in the quote you gave, the cannon only disappears if it runs out of HP or time, or if you actively dismiss it. If you fall unconscious or even die, there is no rule that says the cannon would disappear, so it doesn't.
The next line answers the rest of your question:
On each of your turns, you can ...
The answer provided states that RAW but you may want to clarify with your DM.
Personally regarding spells that remain in play like this as a DM I take it on a spell by spell basis and what makes most sense if a player falls unconscious or dies and then communicate that to my players up front. But I have played at tables where the DM explicitly state’s that ...
This works normally by a strict reading of the spell
Sending (PHB, 274) doesn't actually require the creature to be conscious. It only requires that they have a certain intelligence.
Because there is no requirement for being conscious or awake, then we can read the spell to function as-is in terms of being able to send a message and allowing the recipient to ...
Up to the DM, but RAW no
Does it mean the creature still benefits from its dexterity, both in terms of mechanics and in-game world?
An unconscious creature does not use its dexterity narratively, but in terms of mechanics its AC does not change. This discrepancy was explicitly taken into account in previous versions. For instance, 3.x version had three ...
The target is most likely unconscious until the end of their next turn
The feature in question states:
[...] a creature within 30 feet that looks at the prismatic beetle swarm must make a successful DC 13 Wisdom saving throw or be blinded until the end of its next turn. If the saving throw fails by 5 or more, the target is also knocked unconscious. [...]
No, if the inability to move as a result of being Unconscious includes all bodily movement
your instinctive agility lets you dodge out of the way of certain area effects
Dictionary Definition of Dodge
an act of evading by sudden bodily movement
An unconscious creature is incapacitated (see the condition), can’t move or ...
Potions can be administered to unconscious creatures
The DMG section which give the general rule for potions includes (p. 139):
Drinking a potion or administering a potion to another character requires an action.
With no mention of the character/creature needing to be conscious. That particular matter is further clarified in the Sage Advice Compendium:
Depending on what consititues a knock-out for you, the Sleep spell is ranged, renders the target unconscious and since it doesn't deal damage you don't need to worry about having to stabilise the target. of course, the difference is that the target isn't on 0HP and the capability of the target to recover quickly from being unconscious might ...
A magical spell doesn't actually ask about your willingness. The information is always gathered directly from the mind by magical means. As the information is extracted directly from your subconscious when you are conscious, why wouldn't it also extract it directly from your subconscious when you are unconscious?
Moreover, both Resurrection and True ...
Depends on reading of the rules
The answer is "yes" if "automatically fails a saving throw" counts as "making a saving throw". However, people at many tables read "automatically fails a save" as "isn't allowed to make it". In this case, the requirement of Evasion won't be fulfilled:
you are subjected to an ...