D&D 5E Forced movement into difficult terrain

[Mistwell]

Interesting rules question we ran into last night, while playing in Forge of Fury.

Situation is as follows. There is a Roper. It is centered in and surrounded by an field of entanglement (from a wand of Entangle).

The Roper grabs a PC exactly 25 feet away from a space adjacent to it, and tries to reel the PC to the adjacent space so it can bite the PC.

The Roper's Reel ability allows it to drag the PC exactly 25 feet.

Can it do that, through the difficult terrain of the entangled area? Or does the double movement requirement to enter that difficult terrain mean it can only drag the PC 20 feet to the edge of the difficult terrain, and then stop because it does not have the 10' remaining to move the PC that 5' in the difficult terrain?

 

[Lucas Blackstone]

Technically I believe it can't finish the forced movement since movement still costs double as you already stated. I don't know of any rules for forced movement that change that.

 

[Storyteller Hero]

The rule is apparently left to DM discretion, probably due to the fact that the source of forced movement and the type of difficult terrain can vary in nature.

For example, forced movement due to being tossed through the air versus forced movement due to being pulled by the arm.

 

[Sorcerers Apprentice]

The image of a Roper trying to pull a PC stuck on some nasty roots is just good, so in this case I'd rule that the difficult terrain would inhibit the forced movement.

If the difficult terrain was caused by slippery ice, caltrops or something like that I might rule differently.

 

[Geeknamese]

The rule is apparently left to DM discretion, probably due to the fact that the source of forced movement and the type of difficult terrain can vary in nature.

For example, forced movement due to being tossed through the air versus forced movement due to being pulled by the arm.

Every creature has a speed whether it be walking, swimming, climbing, flying, burrowing, etc. Difficult terrain affects the speed of creatures. Forced movement is not a speed so it is not affected by difficult terrain. Now if it’s an ability that forces an enemy to use their “move” then I would apply difficult terrain to that.


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[Mistwell]

Every creature has a speed whether it be walking, swimming, climbing, flying, burrowing, etc. Difficult terrain affects the speed of creatures. Forced movement is not a speed so it is not affected by difficult terrain. Now if it’s an ability that forces an enemy to use their “move” then I would apply difficult terrain to that.


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That seems like an easy interpretation to exploit. If a PC has an ability to move things with forced movement, they could use it to move allies across difficult terrain at no penalty. Forced movement does have a speed by the way: in this case, the speed is set to 25 feet per round. Not sure what about "move" and "25'" wouldn't be the same as "speed" as opposed to something else?

 

[5ekyu]

Have not checked sage for this.

"You move at half speed in difficult terrain — moving 1 foot in difficult terrain costs 2 feet of speed — so you can cover only half the normal distance in a minute, an hour, or a day." PHB.

Now, some forms of involuntary movement are not speed but just movement - dragged, repelled etc. I do not believe the diffter half applies there.
Other forms of involuntary movement, like say when you have to take reactions and move away "up to your speed" are using speed and would be subject to your diffter penalty - its just you moving at someone else's compulsion.

As for having a PC with a mover-others ability - sure that works to get them moved on your action through difficult terrain in addition to their normal speed on their turn... but that can happen in normal terrain too. Not really seeing it as an exploit - just a use that provides extra benefit when combined with circumstances.

i mean, pushing an enemy back 15' in a difficult terrain means they take 30' to cross back... better for you... just like knocking them 15; back when a ledge is 10' behind them is also good for you and bad for that coyote.

 

[Storyteller Hero]

Alternatively since difficult terrain applies to a [cost] in speed, one might argue that forced movement is not affected because a creature's speed is not being "spent" by the forced movement.

The counter argument might be that the effect of forced movement is "spending" the [cost] from its own total.

 

[Ovinomancer]

That seems like an easy interpretation to exploit. If a PC has an ability to move things with forced movement, they could use it to move allies across difficult terrain at no penalty. Forced movement does have a speed by the way: in this case, the speed is set to 25 feet per round. Not sure what about "move" and "25'" wouldn't be the same as "speed" as opposed to something else?

Any of the forced movement effects I can think of either cost higher level spell slots or also cause damage, both of which are enough of a tradeoff that I don't really see this as exploitable in the usual sense of the word.

 

[Kinematics]

The Roper's tendrils have a reach of 50'. The Roper can pull a grappled target "up to" 25' towards it. That means it could conceivably drag the target less than 25'.

Given that movement ends at the end of each of the Roper's turns, even after a 25' move, and that the PCs would be affected by anything else they moved through (eg: Fire Wall), I would rule that difficult terrain that impedes movement (as opposed to difficult terrain like ice that messes with balance and leverage) would have its normal effect on any target being dragged.

I'd probably round up, though, and allow 15' of drag, if you're only working with the nearest map square.

This assumes the Roper is dragging the target along the ground (which seems the more reasonable assumption). If the Roper did something like yank the target into the air, so that they flew above the difficult terrain before landing in the new rest location, then I'd say that difficult terrain penalties did not apply.