Does reducing a character’s max HP with a spell also reduce the “negative HP” threshold needed to cause instant death?

Here’s my situation: In a fight with a group of vampire thralls, the party’s wizard got caught in a corner and was being savaged by vampire bites, his max HP dropping from 24 to 11. They fended off the vampires, but the wizard was at 3hp (He refused to be healed by the cleric due to his character’s hatred of religion and gods). He activated a trap collapsing the temple, and ended up getting hit by a falling chunk of stone ceiling, taking 15 damage (the rock rolled better than any of the vampires).

Now, the wizard is reduced to 0 hp, with 12 damage left over. The cleric’s player says that exceeds the wizard’s current max hp of 11, causing insta-death. The wizard’s player argues that the death threshold for negative HP isn’t affected by max-hp-reducing spells, claiming that would make those kinds of spells more powerful than intended.

I have stories planned in either case, but I’d rather be certain that I’m following the rules.

Is the threshold for instant death based on current max hp or normal max hp?

What happens when you heal someone who is under the effects of Feign Death in response to Harm?

Here is a hypothetical scenario:

  1. Have Harm Cast on a player (reducing the maximum hit points)
  2. Cast Feign Death on the player, suppressing (not removing) the effects of the disease (not healing, but restoring the maximum hit points they have)
  3. Heal them (now that their maximum hit points are no longer reduced)
  4. Wake them up…

Does their hitpoint stay as they are (at maximum), or are they reduced back down (effectively taking damage again)?

Feign Death:

If the target is diseased or poisoned when you cast the spell, or becomes diseased or poisoned while under the spell’s effect, the disease and poison have no effect until the spell ends.

Harm:

If the target fails the saving throw, its hit point maximum is reduced for 1 hour by an amount equal to the necrotic damage it took. Any effect that removes a disease allows a creature’s hit point maximum to return to normal before that time passes.

Does a Sea Hag’s Death Glare work on a creature that is averting its eyes?

The Sea Hag has a special action called Death Glare:

Death Glare. The hag targets one frightened creature she can see within 30 ft. of her. If the target can see the hag, it must succeed on a DC 11 Wisdom saving throw against this magic or drop to 0 hit points.

Does this work on a target that is averting its eyes?

Is a caster of Gentle Repose aware that a creature under the effects of Feign Death is an invalid target?

Alice (a wizard) & Bob (class unspecified), are planning an elaborate prank on Carol (a cleric). Alice casts Feign Death on Bob, and then wails about how he has been slain by a horrible monster/curse/whatever. Carol, who is, for some reason, friends with these jerks, comes running. Carol does not routinely prepare resurrection spells; instead, she casts Gentle Repose on Bob to preserve him for tomorrow, when she will prepare an appropriate spell to bring him back to life.

Is Carol aware that Bob is not a valid target for the Gentle Repose spell (since he isn’t actually dead), either before or after attempting to cast the spell?

From the PHB, p140:

Feign Death

You touch a willing creature and put it into a cataleptic state that is indistinguishable from death. For the spell’s duration… the target appears dead to all outward inspection and to spells used to determine the target’s status. ….

From the PHB, p215:

Gentle Repose

You touch a corpse or other remains. For the duration, the target is protected from decay and can’t become undead. …

Does a character automatically fail one death save when they drop below 0 hit points?

Hey guys so I have a question regarding death saves and if anyone knows an official source that can determine this.

So according to my dms interpretation of the RAW, if an attack brings you below zero hit points, it not only knocks you unconscious but also inflicts an automatic failed death save from that same attack.

And I to this point was under the idea that the attack that brings you below 0hp as long as it doesn’t also do your max health in damage after the fact then you are simply unconscious. And then all damage received after that inflicts auto fail saves (crits inflicting 2)

Is my interpretation or my dms interpretation correct and is there an official source or creator that has spoken on the matter?

Assassin’s Death Strike Critical?

This is a question regarding the double damage of the Assassin’s Death Strike.

Let’s say a 20th level rogue uses the Sneak attack feature on someone, it is a critical and it fails the CON save for Death Strike. Would the damage be an additional 40d6?

Follow up question. Say that the Rogue in question had purple worm poison on the weapon in which it made the attack. Would the both the critical and Death Strike apply to it, or only one?

Another follow up question: Say the Rogue was using a Giant Slayer Shortsword and the target was a giant. If the giant failed the DC for Death Strike and it was a critical hit, would the 2d6 damage dice be doubled or quadrupled?