… The more likely my players are to squish ’em.
We’re gonna be fighting a few giants in the coming days. Ogres, ettins, trolls, hill giants, stone giants, frost giants, cloud giants, ogre magi, athach, hill giant wereboars, giant rats, giant ants, giant scorpions, bigger giant scorpions, you know. The usual.
What are the 5e rules about Big Things?
First, official rules. A medium character can move through the space of a huge character as though it were difficult terrain, and vice versa (PHB 191); you can’t end there. Squeezing (PHB 192) is difficult terrain, gives disadvantage on attacks and dexterity saves, advantage on attacks against yourself. You can’t grab someone more than one size larger than you.
The phrasing on opportunity attacks is “leave a threatened reach”, so squeezing provokes, as does this size maladjustment bully/sneak movement thing.
Second, nearly-official rules from the DMG (page 271 ish) which we are using anyway and house-ruled modifications.
Climbing onto a bigger creature. You may take this action any time you could initialize a grapple. Make an Athletics or Acrobatics check contested by the giant’s Acrobatics. If you win, you enter its space and cling; while in this state, you have advantage on attacks against the big ‘un (and move with it); the big guy is now difficult terrain for you. Breaking from the DMG: Each time you are hit while climbing, you must repeat your athletics or acrobatics check (your choice) against a DC of half the damage or 10, whichever is higher, or else fall from a height equal to the space of the creature; if the creature grabs you you are automatically dislodged. Also breaking from the DMG: While you are climbing, you double weapon dice on melee weapon damage to your target, as long as you have been climbing for a number of rounds equal to your difference in sizes.
Creatures can Trample. As an action on its turn, a creature may roll, stomp around, slap the ground; each creature smaller than the trampling creature in its space must make a dexterity save or take bludgeoning damage by trampler’s size; a successful save results in half damage.
- tiny or smaller: N/A
- small or medium: DC 10, 1 damage + str mod
- large: DC 12, 1d6 damage + str mod
- huge: DC 15, 2d6 damage + str mod
- gargantuan: DC 18, 3d6 damage + str mod
Creatures take this action as a reaction to falling prone. Some creatures deal differing amounts of damage or differing save DCs. If the creature can’t use the ground as a backscratching post, they may not be capable of trampling.
Creatures can Overrun and Tumble. As a bonus action, a creature can make an athletics (this is an overrun) or acrobatics (this is a tumble) check, opposed by a single creature’s athletics or acrobatics (their choice). If the attacker succeeds, they can move through the target’s space once during their move. Note that if they want to do this as a full action, they can shove instead of overrun, knocking the victim prone and allowing movement through their space. Some creatures (horses) get to trample when they overrun for free.