Both of these are DM calls.
So I'm wondering if a character could get drunk while wearing a PoPAP? There's no "drunk" status condition in D&D 5e, but drunkenness is caused because you've consumed enough alcohol to poison yourself, however slightly.
The problem here is that (outside of things that deal Poison damage or grant the Poisoned condition) there isn't any really great definition of poison. "The dosage makes the poison," and even water can cause intoxication and death in sufficient doses.
We usually bunch things that kill us with a "small" dose into the poison category, and things that kill us with a "large" dose into the not-poison category, but there's a lot of leeway in the middle.
Things that are immune to poison being immune to alcohol is a common trope. Alcohol isn't necessary for us to live, and has a variety of negative consequences. Thus, poison.
On the other hand, the effects of alcohol are pretty mild in typical dosages. It's unlikely to kill you, and may not even have a significant impact on you if you consume it slowly. Thus, not poison.
Which way the magic judges, is up to your DM.
Like for instance, if someone put spider venom in their food, would they know the food was poisoned when they ate it?
I think the general rule for spells applies well enough here. For spells, it works like this:
Unless a spell has a perceptible effect, a creature might not know it was targeted by a spell at all. An effect like crackling lightning is obvious, but a more subtle effect, such as an attempt to read a creature's thoughts, typically goes unnoticed, unless a spell says otherwise.
So, does the spider venom have a specific flavor, smell, or texture? The character can still discern that. If not, then the character doesn't get a "your amulet of poison has protected you" warning.
Of course, your DM could just as easily rule that you can feel the magic working. That there's a tingle in your stomach as the poison is attacked, or that the periapt glows, or similar.
Blackrazor wins ... probably
Ring
If you die while wearing the ring, your soul enters it
Blackrazor
If this necrotic damage reduces you to 0 hit points, Blackrazor devours your soul.
Since being reduced to 0 hit points doesn't usually kill you, then Blackrazor would devour your soul.
PHB, p. 197:
When you drop to 0 hit points, you either die outright or fall Unconscious, as explained in the following sections.
Massive damage can kill you instantly. When damage reduces you to 0 hit points and there is damage remaining, you die if the remaining damage equals or exceeds your hit point maximum.
If damage reduces you to 0 hit points and fails to kill you, you fall Unconscious.
Instant Death
It is unlikely, but technically possible that the necrotic damage from Blackrazor could instantly kill a character. I can think of a few conditions that might make this more likely:
- Low level character might have fewer than 10 maximum hit points
- A character might gain a vulnerability to necrotic damage
- A character may have had his/her hit point maximum reduced by life draining attacks from a wraith or other source
In any case, the key part of the rules regarding dropping to 0 hit points is:
When damage reduces you to 0 hit points and there is damage remaining, you die if...
So, do you drop to 0 hit points, and then die? Does Blackrazor swallow your soul?
Your DM will have to resolve this question. To the best of my knowledge, this is not explicitly outlined in the rules, nor has it been officially answered.
For guidance, your DM might consider this answer found on page 13 or the Sage Advice compendium:
If the damage from disintegrate reduces a half-orc to
0 hit points, can Relentless Endurance prevent the orc
from turning to ash?
If disintegrate reduces you to 0 hit
points, you’re killed outright, as you turn to dust. If you’re a
half-orc, Relentless Endurance can’t save you.
The Relentless Endurance racial feature, PHB p. 41:
When you are reduced to 0 hit points but not killed outright, you can drop to 1 hit point instead.
It is possible that this Sage Advice ruling indicates that even though Relentless Endurance would put you back to 1 HP, the effect of Disintegrate, triggered by being reduced to 0 hit points, is still resolved.
That would imply that, when a character is reduced to 0 hit points, you resolve all of the effects that would happen as a result. In our case, one of those is instant death, and one is from Blackrazor. After resolving both conditions, the character is dead, and his/her soul has been swallowed by Blackrazor.
The effect of the ring cannot not be resolved until after the character is dead. At that point Blackrazor has already swallowed his/her soul.
But in the absence of explicit rules or an official answer, the decision ultimately rests with the DM.
Best Answer
By strict RAW, it would seem that the ioun stone grants all the benefits of the ring, except with a lower healing rate.
Contextually, "works like a ring of regeneration", with no colon- or dash-separated clause to restrict it, does in fact include everything. The following sentence restates the key limitation for clarity and rephrases it to apply to the stone instead of the original ring (which wouldn't make any sense).
While the normal rationale for the immunity to bleeding damage that the ring gives can be thought of as a logical outcome of the constant healing, it's given as its own feature, so it applies without regard for order of operations or any other exceptions: the wearer is not merely cured of any bleeding at the start of each turn, but cannot take any damage from that. As such, it still applies the same way to the ioun stone, even though the stone does not heal nearly as often. (This can be justified in fluff as simply being such a slow constant healing that it only adds up to a single point every ten minutes, but in any case the RAW seems clear enough.)
From a standpoint of balance, which is certainly not a standpoint of RAW but can at least inform houserules, the ioun stone's additional abilities are not nearly so imbalanced as one might think. Bleed damage is not unheard of, but neither is it all that common, and limb removal does not, as far as I know, actually have any rules to enable it. So charging 20,000gp instead of 90,000gp for 1/100 the healing rate isn't too cheap. If anything, it's really not that great a bargain, and the original ring cost a pretty penny anyway.