Fighting on a Huge Beast's Back?

[raumac]

I tried searching the Suggestion/House Rules/Homebrew section but did not find anything on this. If this has already been covered, just point me to that link.

If this should just go under Advice, I can move it there.

<end disclaimers>

Are there rules for standing on, and attacking, a huge creature? Something like running up an elephant and attacking it while on its back.

Why do I ask?

We are at the end of Wake of the Watcher, and giant creature has just appeared in the Mi-Go underwater lab. It can apparently fly, so now we can't reach it (and suspect arrows will bounce off it).

I'd like to spider climb up the walls/ceiling, then drop down on the beast and hack at the tentacles to try and free our cleric.

Would this be a kind of grapple? A series of Acrobatics checks to maintain balance while attacking? A series of Strength checks to hold on while attacking?

If this has come up before (pretty standard attack mode in fantasy battles against giant creatures), I am curious how others have handled this.

I asked my GM, since we continue this battle on Thursday, and he said to check the Forums on Paizo to see if I could find anything. If not, he will just make something up, but wanted to see what others have to say.

Thank you.

[Bjørn Røyrvik]

Oooh, a lot of situational modifiers here.
First of all, shape and composition of the back. If it's flat and rough-skinned to allow good grip, it's a lot easier than if it's very sloped and slimy and smooth

Secondly, is the creature actively trying to attack the thing on its back? That would make close to impossible, at least if creature can reach on its back, roll over or something similar. Is it mostly moving slowly and at a set pace or is it jumping and jerking about?

Since I don't know what monster you are facing, I can't give my opinions on a base DC, but I would handle it like this:

* Standing on the back of a creature Acrobatics (exact DC depending on issues metnioned above. Vs.a creature actively trying to knock you off, Acrobatics vs. CMD each round. Cannot hold on if target rolls over in any way

*Holding on to something to attack: Climb check vs CMD, but treat as fighting while climbing. Can hold on if targt rolls over, but must make a new check to succeed.

[Threeshades]

I have a very long writeup of detailed rules for crawling round on larger enemies and stabbing them in the valuables. Right here

At the end of the page you also find a strongly simplified version made by Evillincoln.

[raumac]

Thanks for the quick replies! I like your points Bjorn, and I will check out your write up Threeshades!

Thanks again!

[Cyrad]

One of my players has a habit of jumping and mounting onto any Huge or larger creature he's fighting. I ruled that doing so is considered grappling except the target creature only gains the entangled condition. If the creature has four legs or is larger than Huge, then the target only suffers the entangled condition with respect to the grappler.