Maximum HP and Damage

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D&D handles HP slightly differently than most games. The key difference is as follows: The game treats Maximum HP and Damage as independent variables, and Current HP as purely dependent.

This page does not actually change any rules, rather it clarifies them and points out some oddities.

  • A character’s maximum HP is equal to the sum of MAX (1, Hit Die Roll + CON Mod) over all the character’s Hit Dice. (note: this is more restrictive in a beneficial way than saying that a character’s Max HP can never go below his HD. Consider a level 5 character who has D8 HD and +0 con. He got the max on the first roll (8) and 1 on all subsequent rolls, for a total HP of 12. If he takes CON damage, he can ONLY lose HP from the first HD roll, so it would take 14 CON damage (enough to kill him) to get him to max HP=5, even though if you subtracted 1 HP per HD per 2 con damage, you’d expect it to only take 4 points of CON damage. In short, low rolls act as a buffer.)
  • A character’s damage is equal to the total amount of damage it has received (this number can be reduced via Cure spells and the like).
  • A character’s current HP is equal to his maximum HP minus his damage.
  • Any affect that stipulates a change in HP implicitly means “Max HP” unless explicitly qualified with “current” (unless this clearly and severely breaks logic. For example, all the rules in the combat section about acting at 0 to -9 HP, natural recovery, etc, should really be talking about changing DAMAGE, not HP!)
  • A Familiar’s Maximum HP is ½ the master’s Maximum HP. The familiar’s damage (and therefore current HP) is tracked individually, of course. This effectively means that changes in constitution of the master change the Familiar’s HP, but changes to constitution of the familiar do not alter the familiar’s HP.

Specific Examples:

  • A Wizard (call him Harry) is level 11, and has a Constitution score of 12 (CON mod +1). Serendipitously, every single Hit Die that he rolled rolled the max (4). He therefore has a Max HP of 55. He also has a familiar, for example’s sake lets say an owl (Hedwig?). Hedwig has a max HP of 27. Let us assume that in the course of a fight with an evil wizard (Shall we call him Tom?), Harry has taken 43 damage and Hedwig has taken 10. His current HP is therefore equal to 12, and Hedwig’s HP is 17. Harry’s friend (Ron?) casts Bear’s Endurance on him, increasing his Constitution score to 16, and his con mod to +3. Harry’s HP max is (temporarily) 77. He has still taken 43 damage, so his current HP is 34. Hedwig’s max HP is still equal to half of Harry’s, so it becomes 38. Since Hedwig has taken 10 damage, her current HP is 28.
  • Instead of Bear’s Endurance, presume that Harry was subject to 4 points of CON damage (everything else held constant). His Maximum HP drops by 2 per HD, so becomes 33. Since he has taken 43 damage, his current HP is -10, and Harry dies. For the instant before Harry dies (and Hedwig reverts to a natural animal), Hedwig’s HP max becomes 16, and her current HP is therefore 6.
  • A Wizard has 20 HP. His familiar therefore has 10. Assume the familiar has a CON score of 10. Someone casts Bear’s Endurance on the Familiar. The Familiar’s HP (current and max) is unchanged, since his maximum is always ½ the master’s, and neither that nor his damage has changed.
  • Same as above, but the Familiar instead takes 4 CON damage. His HP (current and max) remain unchanged.
  • Same as above, but the Familiar takes an additional 6 CON damage (total of 10 CON damage). The familiar has a CON score of 0, and dies (despite his HP not changing)
  • A Wizard at level 1 dies so many times that he ends up with a con score of 1. He therefore has a max HP of 1. His familiar, therefore, has a max HP of 0 (½ of 1, rounded down), and can therefore never take strenuous actions1.
  • A Wizard at level 11 has 44 HP, and has taken 32 damage (current HP=12). His familiar (22HP) has taken 21 damage (current HP=1). The wizard then takes 4 points of CON damage. Specific order of operations:
    1. Con damage reduces master’s Max HP (44 becomes 22)
      • Con reduced HP propagates to Familiar (22 becomes 11) (simultaneous)
    2. Calculate current HP of master (22 Max HP – 32 Damage = -10 Current HP)
      • Calculate current HP of familiar (11 Max HP – 21 damage = -10 Current HP) (simultaneous)
    3. Deal with HP changes of master. Master dies.
      • Deal with HP changes of familiar. Familiar dies. (simultaneous)
    4. Deal with death of master. Familiar is (posthumously) released from service
      • Deal with death of familiar. (simultaneous)
      • NOTE: Since the familiar died before it was released, the master does not lose XP for releasing the familiar. Since the familiar does not die strictly before the master (but rather simultaneously), the master also does not lose XP for the death of his familiar.

1 Conversation extracted to not break the flow

Really? Doesn’t the minimum of 1 hp apply here too? Cadin

We are not sure. Technically, there IS no min of 1 HP in the rules. There is a min of 1 per HD, BUT this breaks on familiars. Since the familiar’s HD is counted as equal to his master’s (including any racial HD or non-sorc/wiz class HD), this gets you in the sticky situation where his max HP is ½ the masters AND his “minimal max HP” is equal to the master’s level. For example, say a master had 10 HD, but such an abysmal con score that each HD was worth 1 HP (so he had 10 HP) – we’d be in a conflicting case where the familiar needs to have 5 HP (½ master) AND 10 HP (min 1 per HD). And we don’t really want a level 10 familiar having the same HP as his master (of course, that level 10 wizard would die if anything looked at him the wrong way!)... The most logical thing to do, then, is to say that Familiars are a special case, and that they use straight math from the Master’s HP, which gives them an implicit lower bound of FLOOR (HD / 2), which for 1HD is 0. Ethan MAY correct this, I hit him with that when he was tired and his response was, and I quote, “XD. That’s the only reasonable way to express what I’m feeling right now. XD.”.... -dylanryan

Yeah, there’s nothing I can see that would prevent a sufficiently stupid unlucky wizard or sorcerer from winding up with a 0 max HP familiar. btw, my comment wasn’t because I was tired, it’s because it was so amusing in a “my brain hurts” way that I couldn’t think of any other good way to respond.Ethan

Also, remember that Venerable age absolutely annihilates con scores. Given that sorcs and wizards have D4 HD, you’d only need a -3 con mod to guarantee 1 HP per HD. With Venerable having a net -6 con score, any wizard or sorc with CON of 11 or less in adulthood will end up with HP=HD at venerable age, so it is good to know how to deal with their familiars! -dylanryan

Maximum HP and Damage

Wings of Redemption dylanryan