Give the player a message when death is imminent

[Mapkos]

My last couple of deaths have been when an enemy I had faced multiple times before, or for the first time, took over 50% of my health in a single attack. I had no idea that it was possible, and would have reacted very differently if I knew it could.

I suggest adding a message whenever a single enemy in line of sight can kill the player in a single attack, something like:

You feel as if your life is hanging by a thread!

It would only be displayed once per encounter, never when they are already recieving low HP warnings, and could have varying degrees of urgency based on the probability that they can kill you.

An alternative solution to the same problem, is to leave the player with a single HP when an enemy does more than 50% of their max HP in a single hit. Or maybe make this a racial feature.

Of course when an enemy is described as extremely dangerous, the player should be wary, but not all extremely dangerous monsters can kill you in one attack, or the player might believe they can not be attacked from their current position. Also, some weaker enemies might easily kill a mage, even if the player has killed dozens of them before. This message would make the game seem much more fair, since if an enemy does one-shot you, at least you were warned about it.

[VeryAngryFelid]

It will result in message spam for Felid and Spriggan.

[Mapkos]

It will result in message spam for Felid and Spriggan.

It doesn't need to be a show more message and if it only happens once for a group of enemies I doubt it would be that spammy.

[Psieye]

I'm not sure a message is the right solution, but it's certainly a thing that streak-minded veteran players always have such thoughts in mind: "can this one-shot me if all the dice line up?"

Thing is, the dice really do have to line up. Most new players will ignore the feedback after a while because 99% of the time it doesn't manifest.

[duvessa]

Most of Crawl's damage distributions have too long and thin a tail for this to be useful for its intended purpose. An 8-headed hydra or an alich crystal spear can do up to 144 damage in one action, but that's so improbable that it has never happened and probably will never happen. Even an ogre with a +0 great mace will only do its max damage on 0.35% of attacks, and that's before AC makes that number even smaller.
It would also have to either leak information or be outright wrong, since some monsters have variable spell sets and any weapon-wielding monster's weapon could be enchanted.

[Mapkos]

Most of Crawl's damage distributions have too long and thin a tail for this to be useful for its intended purpose. An 8-headed hydra or an alich crystal spear can do up to 144 damage in one action, but that's so improbable that it has never happened and probably will never happen. Even an ogre with a +0 great mace will only do its max damage on 0.35% of attacks, and that's before AC makes that number even smaller.
It would also have to either leak information or be outright wrong, since some monsters have variable spell sets and any weapon-wielding monster's weapon could be enchanted.

An example that happened to me is the first time I fought a Hellephant, I was in the abyss. I thought I was far enough away from it, had multiple strong summons between it and me, and had about 75 HP. But I got killed the turn after I saw it because it's fire breath did 90 damage. After looking it up, I saw it had around a 20% chance to kill me. This is something I couldn't have been aware of without looking up the range and damage outside the game.

It just needs to be a rough estimate, so it could ignore things like enchantments, calculate for all possible spell sets, and as I suggested, give a variable message based on probabilities. For example:
<5% : No message
5-10% : You feel that your life is in danger.
10-20%: You feel that your life is in grave danger!
>20% : You feel as if your life is hanging by a thread!!!

[Nekoatl]

The first time you encounter any monster, you should immediately stop and examine it.

[VeryAngryFelid]

The first time you encounter any monster, you should immediately stop and examine it.

It does not help. In-game description does not show how much damage the monster can deal with its attacks or spells.

We had a similar thread recently, devs seem to recognize the info would be useful but unfortunately it is very hard to do from technical point of view and they prefer to display no info when they cannot display precise info.

"Info leak phobia" is the worst thing that prevents crawl from becoming an even better game

[ion_frigate]

Most of Crawl's damage distributions have too long and thin a tail for this to be useful for its intended purpose. An 8-headed hydra or an alich crystal spear can do up to 144 damage in one action, but that's so improbable that it has never happened and probably will never happen. Even an ogre with a +0 great mace will only do its max damage on 0.35% of attacks, and that's before AC makes that number even smaller.
It would also have to either leak information or be outright wrong, since some monsters have variable spell sets and any weapon-wielding monster's weapon could be enchanted.

An example that happened to me is the first time I fought a Hellephant, I was in the abyss. I thought I was far enough away from it, had multiple strong summons between it and me, and had about 75 HP. But I got killed the turn after I saw it because it's fire breath did 90 damage. After looking it up, I saw it had around a 20% chance to kill me. This is something I couldn't have been aware of without looking up the range and damage outside the game.

It just needs to be a rough estimate, so it could ignore things like enchantments, calculate for all possible spell sets, and as I suggested, give a variable message based on probabilities. For example:
<5% : No message
5-10% : You feel that your life is in danger.
10-20%: You feel that your life is in grave danger!
>20% : You feel as if your life is hanging by a thread!!!

Serious question: is this feasible from a performance standpoint? Remember we aren't just considering one user's system here, but rather public servers that can occasionally have hundreds of simultaneous players. Since monsters can wield weapons, you're probably looking at having to calculate/simulate the damage distribution for every monster as it's created/comes into view, and then having to compare the player's current HP to the distribution (or breakpoints from that distribution, rather) for every monster in sight, every turn. It seems like a few dozen players in monster-heavy (in particular summon-heavy) areas could really create a huge performance hit. Remember that sputterflies used to be able to cause major slowdown on public servers.

I think it's a much better option to try and add some approximation of max damage to x-v. You could even make it something like:

95%: <55 damage
90%: <48 damage
80%: <36 damage
50%: <20 damage

The numbers could be pulled from an fsim - since the player doesn't x-v monsters all that frequently, it shouldn't be a huge performance issue.