One benefit to all the hoopla about 5e, is that WotC is bringing up topics that I’ve overlooked. This is one that has bothered me for decades but I’ve never addressed here. How do you handle creatures that are only hit by certain weapons (that the party may not possess)?
A gargoyle is a good example. It is only hit by +1 (or better) magic weapons. If the party does not have such weapons, they are completely unable to cause damage through melee or ranged attacks. They have to rely on spells. If the spell-casters are out of spells, they are at the mercy of such a creature. That really doesn’t work for me. It makes gargoyles too powerful. A single creature could decimate an entire village and there is nothing the villagers could do about it (if no one had a magic weapon and there were no wizards around).
One solution is to give these creatures damage reduction instead. This is typically represented by “DR 5/+1” meaning that all physical attacks against the creature have the damage reduced by 5 HPs, unless the damage is caused by a +1 (or better) magic weapon.
In general, I like the idea. However, I do have a couple of problems with it. First off, if you are going to bring in damage reduction, you are opening the door to questions about the whole AC/HP mechanic. Armor should slow you down and make you easier to hit. In exchange, armor absorbs damage (damage reduction). Some groups do play this way (our group has used it before) but the D&D community as a whole has rejected it in favor of the more esoteric AC/HP system that we are all more familiar with. Ignoring damage reduction from armor but then allowing it as a natural ability of certain creatures bothers me. Not enough to not use it, but it bothers me nonetheless.
The other issue I have with damage reduction is that, in some cases, I think that the requirement of a certain type of weapon (magic, silver, cold iron, etc) should be absolute. Take elementals as an example. If you stab a fire elemental with a sword, should it take any damage? If you shoot an arrow at an earth elemental, do you really expect the arrow to hurt it? A requirement of a +2 (or better) magic weapon seems very reasonable to me in this case. I would be tempted to take that further and say that (even +2 or better) slashing/piercing weapons do ½ damage and that any weapon used to attack an earth elemental must make a save versus crushing blow (you are smashing your sword against a rock). These last additions may be a bit much but I can certainly see an argument for their use.
What Actually Happens?
Say you attack a creature with a non-magic weapon, who is only hit by magical weapons. Or you hit a creature with damage reduction but don’t do enough damage to overcome the creature’s damage reduction. What exactly happens? Does the blow bounce off? Does the weapon pass through the creature? Does it appear to do damage but the wound quickly heal itself? Does the attack actually do damage but natural regeneration heals the wound? (This last implies that enough damage done quickly enough could kill the creature before regeneration takes place.)
It doesn’t particularly matter which of these you use, but as a good DM I think it is important to have an answer to this question so that you can adequately describe what exactly the characters witness.
In some situations, I think it is more appropriate to have the creature take ½ damage from certain attacks, regardless as to whether or not the weapon is magical. Skeletons taking ½ damage from piercing/slashing attacks are a good example of this. In fact, most undead could fall into this category.
How do you attack a ghost with a weapon? Imo, ghosts should be completely immune to normal weapons and magical weapons alike, with the exception of “Ghost Touch” weapons that are enchanted specifically to affect creatures not of the material plane. If these weapons extend into another plane (or wherever it is that ghosts exist), I have to wonder if that also means that these weapons aren’t entirely “solid” and maybe don’t do full damage to “normal” creatures who reside fully on the material plane.
If ghosts are immune to non-magic and magic weapons, doesn’t that make them too powerful? Absolutely it does! I use ghosts sparingly and am very mindful of the location in which I place them. Ghosts in my world are bound to a location and can’t travel beyond certain boundaries. I make sure that characters cannot become trapped within those boundaries so running away is always an option.
Everyone “knows” that you need silver bullets to kill a werewolf. I don’t actually allow guns in my world, but the use of silver on lycanthropes seems too fundamental to change. But, like gargoyles, if they are only affected by silver weapons they are just too powerful. This is an ideal use of damage reduction. DR 10/Silver would make lycanthropes difficult (but not impossible) to hit with normal weapons. Silver weapons would completely overcome the damage reduction, making them easy (well, easier) to deal with for a well-prepared party.
Demons and Devils
I like damage reduction for this group as well. Instead of magic weapons though, my demons and devils are susceptible to Holy weapons and Cold Iron. The term “Cold Iron” is merely a poetic term. Cold iron in no way differs from any other iron. Therefore, it is rather silly to assume that it would contain any additional powers. Since I want to maintain the usage of cold iron on demons and devils, in my world I have had it take on the meaning that it is normal iron containing small amounts of another mineral that gives it the ability to damage (or bind) certain creatures.
More On Elementals
According to the book, elementals exist on the material plane only through means of a summoning spell. They remain for the duration of the spell but require the concentration of the summoner to keep them there. Damage against the summoner may break that concentration. In this context, having elementals that are only hit by +2 (or better) weapons isn’t too overpowering. Characters wishing to go to the elemental plane will know this and it is up to them to prepare accordingly.
But what if, like me, you want to include the opportunity that elementals (at least lower level ones) may have natural methods of travelling to the material plane (attracted to certain “hot spots”, etc) and staying indefinitely? In this case, you may have some overly powerful creatures to contend with.
This makes me want to resort to damage reduction for elementals as well. But, as I said earlier, if you shoot an arrow at an elemental, do you really expect it to do anything? Well, maybe. If you do enough damage, couldn’t you chip away at rock? Maybe earth elementals are somewhat susceptible to normal damage (if there is enough of it). Perhaps other elementals have trouble maintaining cohesion away from the elemental plane. A weapon attack may disrupt some of that cohesion. Perhaps it’s a bit of a stretch but that’s the best rationalization I’ve been able to come up with so far.
I like the idea of having elementals on the material plane outside the confines of a summoning spell and I don’t like the idea of invulnerable creatures wandering around. Therefore, elementals with damage reduction seems like a good compromise.
However, Not all elementals have to be created equally. I have separated them into five groups (small, medium, large, huge, and elder). Small elementals, regardless of type, have DR 5/+1, each group thereafter adds five to their DR and adds +1 to the weapon required to overcome damage reduction (up to DR 25/+5 for elder elementals). Unlike other creatures with damage reduction or immunities, elementals are each susceptible to other attacks (such as water against a fire elemental) that keeps the more powerful ones from being an unstoppable force (such as the village-decimating gargoyle discussed earlier).
Resistances and Vulnerabilities
Another approach is to make creatures resistant or vulnerable to certain attack forms or damage types. One application interprets resistance as meaning that the creature takes ½ damage from the listed attack form and vulnerability as taking double damage from that attack form. Another interpretation applies degrees of resistance/vulnerability, so that “Resist Fire 5” means that the creature ignores 5 HPs of damage from each fire-based attack.
I’m not a big fan of resistance and vulnerability as natural defenses. But I think the quantified form works well for magical items and spell effects.