Earth Mastery - What is the "ground"?

Question

An earth elemental has earth mastery,

Earth Mastery (Ex) An earth elemental gains a +1 bonus on attack and damage rolls if both it and its foe are touching the ground. If an opponent is airborne or waterborne, the elemental takes a -4 penalty on attack and damage rolls. (These modifiers are not included in the statistics block.)

Would this be essentially any surface, such that an opponent would either be touching the ground, airborne or waterborne? Or would it need to be a natural surface, precluding masonry, or second stories?

As mentioned in comments, this is also carried over into the Pathfinder earth elemental.

I would also be interested in suggestions for a playable definition, if none exists in the rules set.

Answer 1

Likely, the writers meant "standing on soil or stone"

The RAW is, as you mentioned, unclear. I will be addressing this mostly from a flavour perspective - what would an Earth elemental have affinity with?

Note that by rules as intended, ground is likely not just any surface - the writers are always happy to assume that everyone is humanoids walking around, so there would be no reason to exclude the +1 from the elemental's stat block if it applied in practically all cases. They could just say "-5 when the enemy is flying or swimming" and it would be much simpler. The text implies that there is a state that's not standing on the ground, flying, or swimming.

One source of information we have is abilities that were printed later, with similar flavour. Earth Spell and Earth Power are both feats that let their users draw strength from the ground, and have similar requirements:

As long as you are standing on stone or unworked earth (including normal soil)...

The Stone Dragon discipline from the Tome of Battle has this to say:

Unlike with other disciplines, adepts of this school rely on an external force— the power of the earth and stone—to help power their maneuvers. As a result, Stone Dragon maneuvers can be initiated only if you are in contact with the ground.

The Elemental Plane of Earth - from which these Elementals draw their power - is described in the Manual of the Planes like this:

The Elemental Plane of Earth is a solid place made of rock, soil, and stone...

Answer 2

Three points to consider here.

First.

I think that "Earth Mastery" has a lot of resemblance to mythic power of Antaeus. Similarities are more than passing so that could be inspiration for it. In all versions of this myth I stumbled upon, explanation of Antaeus's power - is his mother Earth aided her son.

We don't have mother Earth (Geya) as planet sized super-elemental in DnD ^ ^ but the core principle could stand: earth elemental is strong on earth because it gains support from some kind of external source... And huh - here comes Planescape (or just Planes) cosmology. Think about Negative Plane, Positive Plane - they had points of connection to Material world. You can find Planescape definition of Plane or Earth or use simpler version like Earth Plane. Place of stone pressure, metals. No wood or air. This could be source of Earth essence that fuels all earth elementals, 'a breath of earth' for them to speak metaphorically in environment that is mostly alien for them - the Material Plane.

Second.

What if their Earth Mastery is a matter of training with navigating through Earth Plane (see links above). In a sense that they are proficient with using everything you can find there - stone, metal, rocks... Not wood. How exactly? Maybe they manipulate themselves and opponent, maybe they hear vibrations... Because they are skilled and evolved to fight in that Earth hell - not a borrowed power, but matter of expertise and skill...

Third.

Earth elemental has an Earth Glide ability.

An earth elemental can glide through stone, dirt, or almost any other sort of earth except metal as easily as a fish swims through water.

What if developers of DnD gave consistent names to abilities of elemental? What if "Earth" part means the same for Earth Glide and for Earth mastery - "stone, dirt or almost any other sort of earth except metal"?

Result:

Generally, considering all three points, I come to think that Earth elemental gets that bonus even if it's second floor of building, provided that floor is made of "stone, dirt or almost any other sort of earth except metal", and this floor is connected to the Earth Plane or greater Earth (which is connected to Earth Plane) by at least a tiny wire of earth (here - including the metal). If you treat source of power for Earth elemental as "2" (as predator with senses and training suited for certain environment) more than "1" (as mythic outsider creature gaining it's power from elsewhere) you could skip the 'wire to the Plane of Earth' part.

Answer 3

The Rules As Written (RAW) are unclear which ultimately makes the decision the DMs.

But, to provide a little insight, I added the Divine Earth Mastery feat, edited for brevity.

The deity gains a competence bonus on attack rolls, damage, and Armor Class equal to its divine rank if both the deity and its foe are touching the ground...

...The deity can also transmute any object made of earth, stone, or metal into a different kind of earth, stone, or metal. The deity can affect any object it can see, but no more than one object per round.

Which references Earth, stone and metal as the things the deity has full effect on, and maintaining the vague "ground" reference for attack bonuses etc. Is it a wording error? did they intend to specify the second part more explicitly? or is that second mention supposed to expand on the term "ground"?

That is a DM decision.

Personally, I would say the elemental gains strength from fighting on materials inherent to his domain, because that seems to be the theme for the other elemental types (fire gains power when fighting in fire, so earth gains power when fighting on earth) so if you are both on earth/metal/stone, natural made or man made, you add the benefit the elemental.

Answer 4

The way I read it -- If the Elemental and opponent are terrestrial they'd get the bonus.

(As a DM, I'd maybe rule otherwise if people were fighting on an exotic material or somebody figured out a way to disadvantage it -- e.g. levitation, fly, wall of force, etc).

It specifically only by RAW disallows Airborne or Aquatic, which makes sense.

Now, if as a DM, you wanted to get more specific -- I'd say Earth, Stone, or Metal would definitely be acceptable for the bonus (and possibly wood, as long as it's not a tree).

Answer 5

The 'ground' would be the largest chunk of mass consisting of natural unworked substance sufficient to produce gravity, even slight gravity.