Editing Tarrasque (section)

===(5E) How to troll the Tarrasque, V2.===
The "[https://dnd-5e.fandom.com/wiki/Actions_in_Combat#Climb_Onto_a_Bigger_Creature climb onto bigger creature]" action abuse (Dungeon Master's Guide, page 271). Though, it may work for all monsters 2 sizes bigger than you, and some monsters 1 size bigger than you.

It works on opposed check: small creature uses Strength (Athletics) or Dexterity (Acrobatics) as it chooses - while large creature uses Dexterity (Acrobatics) when preventing from climbing on, and Strength (Athletics) to displace someone who's already climbed on. Therefore, strong creature (like most big monsters) is easy to climb on but hard to stay on - while agile creature is hard to climb on but easy to stay on.

The parts about climbing on, and then moving around with the creature, and having advantage when attacking it are not a big deal. But, "The larger creature's ability to attack the smaller creature depends on the smaller creature's location, and is left to your discretion."; in other words, it's up to DM if Tarrasque or other large monster can attack someone clinging to/sitting on it. If it can't, then there's all chances what Tarrasque would spend most of the fight dislodging PC's instead of actually attacking; if it can, then it's likely what Tarrasque would attack instead of dislodging due to actual economy (each turn spent to dislodge is turn when monster doesn't attack - while PC's are numerous, and will end up clinging faster than they get dislodged anyways).