Climb onto a Bigger Creature - Anyone use this?

[PeteNutButter]

The rules for climbing onto a bigger creature are on page 271 of the DMG. They aren't extremely explicit, so there is a lot of DM input in how they work.

I just think it'd be awesome to build a character around this idea. Possibly a rogue/bard for that expertise in athletics/acrobatics.

I'd say, a safe bet is that in order to climb onto a creature you have to be two size categories smaller than it. So a halfling can climb onto an ogre, and a human onto a giant. That fits it neatly into the category, "If you can't grab it, you can climb it."

It gives you advantage on attack rolls and the larger creature's ability to attack their parkour annoyance is based on their location. Climb onto things backs and you could potentially be untargetable. They can still try and dislodge you but with a good base stat and expertise... you're fairly safe and it would take their whole action.

Pros:
-Advantage on attacks (not just weapon attacks, so if you feel like casting touchy spells...)
-Potentially unable to be attacked
-Move with the target, so you don't have to worry about those tiny legs or a fly speed

Cons:
-Takes an action as written(not one attack during an attack action)
-Doesn't work against medium or smaller according to my assumption (Maybe be an AT and take Enlarge/Reduce? Tiny Halfling! For some reason this reminds me of cheesy 80s horror movies...)
-Move with the target, so you could potentially get dropped out of the sky or dipped into lava etc.

So what do you folks think? Have you/would you use this mechanic? Do you think the 2 size category assumption is reasonable?

[Laserlight]

A couple of weeks ago my kenku drunken master staggered up the back of a T Rex (which had just eaten our halfling swashbuckler in one bite) and delivered the finishing blow.

We had a barbarian who jumped onto a shadow dragon's face and clamped its jaws shut so it couldn't get another round of dragonbreath. He had to keep attacking to keep his rage up, so he headbutted the dragon.

Back in 4e, my pixie sorc wanted to ride inside the head of our barbarian. He insisted that his head wasn't hollow, although I pointed out that anyone who watched his "tactics" would disagree.

[Lombra]

I do it regularly for style points. It's good for distracting a creature, but it's pretty dangerous. I do it with a shadow monk, which has only +5 to athletics, so with stronger characters it may work even better.

[mephnick]

Our human long death monk used it to great effect in our SKT campaign while it was still going. Climbing around giants hitting pressure points like Shadow of the Colossus. Good stuff.

[GlenSmash!]

I use them.

Even If I didn't have explicit rules for it, it's the kind out of the box thinking I encourage at my table. But the DMG rules work just fine.

I did allow a medium size creature to climb on to a large size, it was a Rothe (co or ox basically). I figured if the character could ride it like a horse, he could climb onto it.

[strangebloke]

I had the party goblin climb on my back and use me as cover whilst shooting arrows. Worked pretty well, IMO. As a side benefit, it meant that he had mobility while not worrying about AoOs because he didn't proc a hit when I moved out of a square. I've also walked into an ambush with the goblin and the halfling riding in my pack. Made for a great surprise when I tossed over my belongings.

Had a barbarian jump onto a cyclops once, and asked if he could expend an attack to hold on to the thing's face while hanging in front of the thing's eye. The thing was blinded and so everyone had advantage on attacks against it.