Arcobatics and Moving Through Enemy Space

[Starfox]

The fluff of the Acrobatics skill mentions that it can be used to move through enemy space:

Make an Acrobatics check to swing from a chandelier, somersault over an opponent, slide down a staircase on your shield, or attempt any other acrobatic stunt that you can imagine and that your DM agrees to let you try.

My emphasis.

This is very ambiguous and leaves things very up to individual discretion. Since moving through enemy space is pretty important, I want firmer rules on it. Additionally, I find that I want this to be possible; we tend to use rather cramped maps and larger critters are very vulnerable to being boxed in. Thus I propose the following house rule:

You can pass through an enemy's space relatively unhindered as long as that creature's size category is smaller than yours. If you end your move in a smaller creature's space, that creature can choose to either fall prone or shift up to it's Speed to a square adjacent to you as a free action at the end of your movement.

You pass through the space of an enemy of the same size as you or larger. This space is considered difficult ground for you. You cannot stop your movement in another creature's space; it you are somehow forced to stop moving within the space of an enemy, you instead end up in the last legal space you moved from.

If you are trained in Athletics, you can perform an acrobatic stunt to avoid the difficult ground penalty, the DC is 10 +5 for each square moved through an enemy's space. On a failure you end up prone in the last legal space.

If you use an effect that allows movement through an enemy's space, that space is not considered difficult ground.

Note that this rule does not mention OAs; those play out as usual. Nor does it differentiate between normal moment and shifting; both are movement rules-wise.

 

[Neubert]

I am not sure if I agree with using a fixed DC. Perhaps add ½-level of the creature which space you are entering to the base DC?

 

[keterys]

I would suggest against the size category restriction. You can't see a halfling or gnome, say, rolling under a giant?

I'd also suggest a scaling DC, rather than a flat one.

I'm very dubious of things like a human being able to move on top of a kobold or goblin and having it fall prone or shift away, especially since a rogue could use that to trigger a fighter's combat challenge. I know you're doing it so that large+ creatures can maneuver around, but I suspect you could figure out a better way.

 

[spinmd]

You can move through an enemy's space if the enemy is two size categories larger or smaller than you, though it does provoke opportunity attacks. PHB 283

So, a halfling can duck under a giant, or a huge creature can push through the medium PCs squares without acrobatic or athletics checks, they just could take some opp attacks.

If a PC wanted to move through an enemy's space of same size or one size category difference, I would make it an acrobatic stunt and use Pg 42 (opp attacks as normal).

 

[KarinsDad]

This came up in our game just 10 days ago.

I am toying with the house rule of:

"The size of the opponent does not matter (for simplicity). The PC makes an Acrobatics check against the better of the NPC's Athletics, Acrobatics, or overall Dex modifier plus 20. If successful, the PC can get through the square. If not successful, the PC uses the movement and remains in the last legal square he was in. The PC still provokes OAs like normal (regardless of success) and this move cannot be combined with a Shift. Moving through an opponent's squares is considered difficult terrain."

Less than 100 monsters in the MM have Athletics or Acrobatics, hence, the DC tends to be Dex+20. So, a 14th level Drider Shadowspinner (somewhat low Dex) would set the DC to 30.

At 14th level, a PC with a Dex of 14 and no Acrobatics training would be +9 and would not succeed without help. A normal Rogue with training and a Dex of 22 would be +18. He needs a 12 or higher (45%). A Rogue with training, a Dex of 22, Skill Focus and a +3 Acrobatics item would be +24 and only needs a 6.

Powers that boost or allow for re-rolls on the next skill check would increase the odds.

And there are many monsters that would be more difficult than this: monsters with higher Dex (the Shadowspinner is somewhat low), monsters that have Athletics or Acrobatics, and higher level monsters.

The idea is to not allow this to take the place of multi-square shifts (like the Tumble power) and not something that is done often, rather the intent is to allow the trained PC (and not most untrained PCs) to sometimes do something cool, but to pay the OA for doing so. And, the intent is to keep the rule fairly simple.


Note: The reason to add Athletics is twofold: 1) An athletically trained creature should be more able to quickly move to interpose (e.g. jump to block), 2) Monsters have an extremely low number of skills, so I didn't want to totally penalize strong creatures that are athletically trained, just not acrobatics trained. I could see that high Str low Dex monsters might not be able to react in time unless they are trained in Athletics, so I did not add raw Str without Athletics into the equation.

 

[BobTheNob]

Im really iffy on allowing it. Players always insist that enemies cant get through there lines cause "we dont let them!", yet when the shoe is on the other foot I get vague nonsense like this quoted at me (ie there vague rules from the book).

To be able to puch "through" an enemy line is a real advantage, and to me, I really want to be more impressed in terms of a characters commitment to his build in order that he achieves this kind of power. A skill check really just doesnt do it for me because there is no commitment : you get the skills at character creation. Just too little price paid for the power for my taste.

I did have an example where the party was up against a "phalanx" of hobgoblens (using there shared defence advantage) our rogue wanted to punch through the line, and suggested that the Tumble utility power should do it. This I didnt mind : The player had invested in the power, which meant they had made a genuine commitment to mobility as a priority. Price paid = reward given. This I allowed.

Skill checks I wouldnt.

 

[77IM]

That is a fine rule, although I find the size restrictions too complicated for my taste (I find little rules nuances like that, even if they make sense, don't add much for me and are often forgotten). I agree with the other posters that the difficulty should scale with level. Pushing someone out of your way by ending in their square is also troublesome -- I would make this cost a standard action and a Strength check, and basically call it a variant bull rush.

I would use the "hard" DC for an encounter of that level (which is 14 + 2/3 the encounter level, +/-1 if you want to follow the chart exactly) to move through an enemy's space as though it were unoccupied. The penalty for failure -- falling prone -- should be enough of a deterrent to keep people from trying this too frequently, even if they have a really good Acrobatics. I'd really love to use the monster's Reflex defense as the DC, but defenses scale in a strange progression relative to skills. :{

-- 77IM

 

[keterys]

Yeah... I think I'd possibly just call it 15 + 1/2 level as the DC and move on from there.

 

[Neubert]

You could give a bonus to the check based on size (or rather size difference), so the rules would work the same for everyone.

 

[Starfox]

Having read this thread and discussed this with my players, this is my current version. It does away with the size difference thingie and lets a successful opportunity attack block movement completely - which you can get around using shift.

Note that this has the consequence of allowing forced movement trough "enemy" squares, something that is not currently allowed.

On the opposed roll question, I find opposed rolls have too widely varying difficulties. I also don't like the idea of a dextrous creature blocking the path more effectively - dextrous creatures are trying NOT to be hit. If anything should increase the DC, its bulk and size. I also prefer to do away with most of the interactivity of this move; by simply declaring it difficult ground, you avoid dice rolling. Only when you really need that last square of movement will you bother to roll.

The group defender protested that this makes it too hard to hold the line, so I added a way to stop this using an existing mechanic. In this way, creatures that are not specialized in shifting will find this maneuver hard and risky.

Also note that elves can use their ability to shift trough difficult ground with this, which makes that ability worth more. Currently, I find that ability fairly useless.

A remaining hurdle for me here is if this should exist alongside the rules that allows creatures two size categories different pass trough each other, or if it should replace that rule. This writeup assumes the two rules will coexist.

You pass through the space of an enemy that is within one size category of you with some risk and effort. The enemy's space is considered difficult ground for you. You cannot stop your movement in another creature's space. You cannot move trough the space of an enemy that has made a successful opportunity attack against you since the beginning of your current turn.

If you are trained in Athletics, you can perform an acrobatic stunt to avoid the difficult ground penalty, the DC is 10 +5 for each square moved through an enemy's space. On a failure you end up prone in the last legal space.

If you use an effect that allows movement through an enemy's space, that space is not considered difficult ground.