[RPG] How large must a creature be for the “Climb Onto a Bigger Creature” action


From the DMG:

Climb Onto a Bigger Creature

If one creature wants to jump onto another creature, it
can do so by grappling. A Small or Medium creature has
little chance of making a successful grapple against a
Huge or Gargantuan creature, however, unless magic
has granted the grappler supernatural might.

As an alternative, a suitably large opponent can be
treated as terrain for the purpose of jumping onto its
back or clinging to a limb.

The first paragraph of the action references the inability of normal-sized PCs from grappling Huge or Gargantuan creatures, but it doesn't clearly state whether the action can only be taken for those creatures, or if it can be taken on simply larger creatures. Throughout the rest of the section, it refers only to the difference between larger creatures and smaller creatures.

This begs the question, can a Medium-sized PC climb onto a Large opponent (think Legolas climbing onto the cave troll in Moria)?

Best Answer

By rules as written, you can only grapple creatures one size larger than yourself (PHB p. 195), so a medium creature can jump on a large and a small onto a medium.

Note that the second paragraph is an alternative, not a variant, so it too is in play. If the creature is larger than you can grapple and is suitably large, whatever the DM decides that is, you can simply use your movement to walk or climb it. The DM would need to decide which and if the creature was difficult terrain or not and if any checks are needed; presumably Dexterity (Acrobatics). Assuming the creature didn't want you there it could try to throw/pull/buck you off, resolve this as an opposed check.

Personally, I think it would be awesome if the players jumped and climbed up the dragon to try and sever its spine. They would too; right up to the point where I say "The dragon drops prone and rolls over you. Time for some saving throws."