What happens if you put a bag of holding in a bag of holding while being in the astral plane?

I know that putting a bag of holding in a bag of holding destroys both and creates a portal to the astral plane, but what would happen if a player chooses to put a bag of holding in a back of holding while being in the astral plane?

Would nothing happen? Would you be transported to a realm of chaos? Any answers would be appreciated!

Proof of Co-Problem being in NP if Problem is in NP using negated output

Given any problem $ P$ that we know of being in $ NP-\text{complete}$ , where is the flaw in the following proof?

Given a problem $ Co-P$ which is the co-problem of $ P \in NP-\text{complete}$ , $ Co-P$ is at least in $ NP$ because the following algorithm can always be given:

Co-P(J):     bool res = P(J)     return !res 

Where $ Co-P(J)$ is the algorithm solving $ Co-P$ and $ P(J)$ is the nondeterministic polynomial algorithm solving P.

Why is this not correct?

Does being “paralyzed” grant the effects of a rest

One of our players got paralyzed for 10 hours by a special dart (homebrew). We were in combat when he went down and were in combat when the effect wore off although they were 2 separate encounters. When he woke up in the middle of the fight we didn’t know whether the paralyzation counted as a long rest so we were unsure whether he had full hp or was still injured from before?

Ways to prevent Counterspell from being cast?

What ways can a character (PC or Monster) prevent an enemy from casting counterspell?

What I can think of so far:

  • Surprise the enemy and win initiative
  • Cause the enemy to be incapacitated (or stunned/paralyzed/unconscious)
  • Provoke the enemy into using a reaction earlier in the round (readied action, opportunity attack, previous spell)
  • Avoid using perceivable spell components
    • Sorcerer subtle spell metamagic
    • Level 20 Druid Archdruid feature
    • Casting a spell with only material components (eg. Minor Illusion)
  • Prevent somatic components
    • The enemy is holding objects in both hands
  • Block line of sight (often interferes with targeting)
    • Spells such as Fog Cloud, Darkness, etc.
    • Physical barriers such as walls or large creatures

Are there any other options available that I am missing?

How can I pull off being two two separate characters at the beginning of a campaign?

I will be playing a Changeling in an upcoming campaign (homebrew setting). I’m interested in hiding not only my race, but also having one or more "retainers" — alternate identities / personas that my changeling can slip into and out of as needed.

The catch is, I wish to conceal (at least at first) the fact that the PC and the NPC retainers are actually a single entity! The most straightforward way of doing this would seem to be observers seeing "both" characters arrive to the starting town at the same time. I would want this to deceive NPCs and fellow PCs.

What magic / mundane / class features do I need to pull off such a deception at level 1? If not, what’s the earliest level you could realistically pull the wool over NPC eyes, solo? The ruse must be able to confound casual observers, but bonus points if it can stand up to additional scrutiny!

I don’t have a set class for this character, but am leaning towards Bard, Rogue, or Wizard. Since I’m trying to fool the party as well, count on no help from them.

Is a lich aware of its phylactery being destroyed?

Let’s say the party who are going up against a lich discovered where its phylactery was and how to destory it. They manage to get to the phylactery without the lich knowing about it and destory the phylactery.

Would the lich be aware that its phylactery had been destroyed? Is there anything in any official D&D publication that states whether or not a lich would know that its phylactery had been destroyed? I’m playing 5e, but lore from any previous edition is welcome if 5e doesn’t have any information on this.

What makes a spell being cast considered to be a {class} spell?

My understanding is that when a spell is known or prepared via one of your class features, or if you cast it via a class feature, it’s considered a “class spell” (sorcerer spell, cleric spell, etc.) for you. If you cast it via some method outside your class (items, etc.), it isn’t considered a spell from your class.

For clarity, some class features care about whether or not a spell is a ‘class’ spell (emphasis mine):

  • Wild Magic Surge for Wild Magic sorcerers can only trigger “[…] immediately after you cast a sorcerer spell […]”.

  • Overchannel for School of Evocation wizards can only be used “when you cast a wizard spell […]”

  • Empowered Evocation for School of Evocation wizards can also only be used on “[…] any wizard evocation spell you cast”.

  • Rod of the pact keeper gives a bonus “[…] to the saving throw DCs of your warlock spells”.

Contrast with a feature like Blessed Healer for Life Domain clerics that just use the language of “When you cast a spell […]”, and you’ll see why I believe there’s an important distinction as to whether or not a spell instance is a ‘class’ spell.

However, comments on this answer made me question where my understanding of what makes a spell instance a ‘class’ spell comes from, and I’m not sure of a concise spot that explains it. What are the rules that govern what is or is not considered a class spell when cast?

Of particular concern is whether or not a spell is, in all instances, a class spell once you’ve obtained it from your class. For example, if you were a wizard that had magic missile both prepared and in your spellbook, would any instance of magic missile you cast be considered a wizard spell, even if it was cast by way of, say, a wand of magic missile?

I want to try being a DM

So sadly, after almost two years, our DM has kinda had a burnout, though that was obvious to us months earlier as our once a week game became one every few weeks to months. Long story short, he’s taking a hiatus, and even if he does come back, it won’t be with these current characters. He specifically said "world", but I would have to assume these characters as well. However, I still heavily love playing with this group, we all started playing online anyways so in person didn’t matter. The problem was that all of us were relatively new to the game, this campaign being our first ever. One of the other players only ever set up one-shots for us but I was hoping to play a full campaign again, this time in the DM’s chair. I’m scared to try though. Should I try my own homebrewed world (still based in the regular mechanics just not any rewritten story) or is there a rewritten campaign I should look into like Ravnica or Sword Coast or something?

TLDR; I want to try DMing but don’t know if I should go with my own world or an existing module.

Does standing up after being knocked prone use half your current or maximum speed [duplicate]

I’m DMing a campaign and one of my players is a monk with 40ft of movement. He got hit by a slow spell reducing his speed to 20ft and was knocked prone. To get up would he have to use his full 20ft as its half his max speed or only 10ft as that’s half his current speed?