Aside from minor rounding errors for very low damage, a monster with x hit points and the insubstantial resistance type is exactly the same as a monster with 2x hit points.

So, why does the "insubstantial" quality exist at all? It seems to have no actual purpose. (If there's a weapon out there that does full damage to insubstantial monsters, it could be modeled as a weapon that does double damage to certain types of monsters.)

  • \$\begingroup\$ And just to be pedantic, insubstantial is more than double health since you round down, making them on average more resistant to multiple, weaker odd-numbered attacks than they are to a single larger hit. \$\endgroup\$ – Frezak Aug 22 '14 at 7:40
  • \$\begingroup\$ A battle is over in what, 4 rounds average, 8 round tops? Did you calculate how much extra damage is likely to resisted by rounding down? It ain't much. \$\endgroup\$ – Snowbody Aug 22 '14 at 15:59
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    \$\begingroup\$ It's more significant in heroic when you look at multiple-target powers. I just ran a Fell taint Void Caller and Defiant encounter (DMG 376) for four L4 players and rounding down probably cost them about 60 HP worth of damage. \$\endgroup\$ – Frezak Aug 22 '14 at 17:02

The reason that insubstantial exists is that not all monsters are insubstantial the entire fight (along with the fact that PCs can gain this power as well). Also some monsters such as the mad wraith have conditions to the insubstantialness (mad wraith takes full effects of force damage). If a monster can turn into mist, go ethereal, whatever during the fight its much easier to model it taking half-damage during the ability than it would be to adjust the hit points up then back down.


Several reasons:

  1. It's good flavor. Sure, we could just numerically simulate the game and drop all the flavor, but that's no fun.
  2. PCs can get the condition from some powers as well, so it's not as though it's constant for a given creature.
  3. Doubling HP and selectively doubling damage means that 50 damage on this particular monster is no longer on the same scale as 50 to the others.


  1. Insubstantial monsters, if they had double hit points, would need double effect from damage resistance, damage vulnerability (possibly), temporary hit points, and healing.
  2. PCs have effects that grant them normal damage against insubstantial creatures; it would be extremely painful to write these out as a list. That's why we have keywords.
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    \$\begingroup\$ I disagree with #1; it's not "flavor" if the players know the monsters' hitpoints, it's metagaming. \$\endgroup\$ – Snowbody Aug 16 '11 at 22:18
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    \$\begingroup\$ @Snowbody Then the problem is clearly the metagaming, not the flavour or lack thereof. \$\endgroup\$ – SevenSidedDie Aug 16 '11 at 23:34
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    \$\begingroup\$ Of course it's flavor. You don't see a ghost and say, "Oh, that's one tough beast and I'll have to do a ton of damage (double HP) to it before it dies." You say, "Hmm.. My weapons probably aren't going to hit that so well. (Half damage)" \$\endgroup\$ – dpatchery Aug 17 '11 at 12:47
  • \$\begingroup\$ ahh, I get it now, thanks for the explanation @dpatchery. \$\endgroup\$ – Snowbody Aug 17 '11 at 14:19

It's a holdover from third edition D&D, where the "incorporeal" property gave a creature a 50% chance to ignore any attack. This was really annoying if you used up a once-per-day ability and it had no effect, so 4th edition changed it to 50% damage.

  • \$\begingroup\$ Do you have a source for this? Or is it just a hunch? \$\endgroup\$ – Pat Ludwig Mar 6 '12 at 7:13
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    \$\begingroup\$ It's a hunch, but a reasonable one. The same creatures that had Incorporeal in 3e have Insubtantial in 4e, and it has a similar effect (50% miss chance vs 50% damage reduction) and meaning (the creature is partially not-there and partially ignores your attacks). \$\endgroup\$ – Joe Dovahkiin Mar 6 '12 at 14:23
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    \$\begingroup\$ D&D 4e also tends to protect PCs from wasting their best powers to a frustrating random miss. Daily powers deal half damage on a Miss, or are Reliable. Monsters no longer have abilities like 50% miss chance or spell resistance. It's reasonable that Insubstantial exists because it's an improvement over 3e's Incorporeal, rather than filling some new design role. \$\endgroup\$ – Joe Dovahkiin Mar 6 '12 at 14:40
  • \$\begingroup\$ Thanks, was just looking to get sourcing information in your answer if it was available. \$\endgroup\$ – Pat Ludwig Mar 6 '12 at 15:19

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