The Battle of the Strings

Setting

You have been caught in the realm of Linnaeus, god of the First Dimension, Length. This is an alien place to higher-dimensional beings such as yourselves, since it consists solely of parallel "Strings" that one-dimensional creatures can travel upon. The guardians of this realm are the Standing Waves, which mindlessly seek to protect Linnaeus and the Strings. During your travels to this realm and your conversation with Linnaeus, you were found by the Standing Waves, and must now fight your way back to the dimensional portal that will bring you out of the First Dimension.

Battle Mat

It is highly recommended to play this battle on a battle mat rather than as a theatre of the mind exercise, due to the abnormal geometry of the fight. The setup in this case is simple--draw three parallel lines (these are the Strings) on the grid through a line of boxes, and arrange pieces representing the player characters in a line along the center of the middle String (allow them to choose the order, or randomly determine it). Then, surround them with Standing Waves on the three Strings, as many as you deem appropriate for their character level and the challenge you wish to provide.

String Battle Rules

While battling on the Strings, rules for combat are modified in the following ways:

Conditions

While fighting on the Strings, all creatures are immune to the prone and grappled conditions. All senses are replaced with 'hearing' vibrations in the strings, meaning that all creatures are immune to being blinded, but being deafened causes a creature to suffer the effects of blindness. Creatures cannot hide or be concealed, and all creatures in the battle know where every other creature is at all times, unless a creature becomes invisible.

Also, when a creature is frightened, rather than simply moving away from the creature it is frightened of, it instead must move so that it "hides" behind a friendly creature, such that the friendly creature is between it and the creature it is frightened of.

Movement

Each creature divides its speed by 10, rounding down, to get its number of Moves (e.g. a gnome wizard would have 2 moves, while a Wood Elf monk might have 6). If a creature uses the Dash action, it gains more moves according to its speed. Each Move can be used to do one of the following:

Slide : Move a single direction on a String. This movement is not restricted by distance (you can move through as many spaces as you want), but you cannot move past a creature on the String.

: Move a single direction on a String. This movement is not restricted by distance (you can move through as many spaces as you want), but you cannot move past a creature on the String. Swap : Change places with one creature that is adjacent to you on a String. If the creature's size causes it to occupy more than one square, you must spend one Move per square of its size to Swap with it (see "Size" section).

: Change places with one creature that is adjacent to you on a String. If the creature's size causes it to occupy more than one square, you must spend one Move per square of its size to Swap with it (see "Size" section). Skip: Jump to an adjacent String, landing at the spot perpendicular to where you jumped from. This cannot be done if there is a creature currently occupying the corresponding spot on the String you wish to jump to.

Size

Since this battle takes place in the First Dimension, creatures always occupy a 'line' of squares on a string, determined by their size in higher dimensions (small and medium creatures occupy one space on the String, large creatures occupy two, huge creatures occupy three, and gargantuan creatures occupy four).

Shoves and Dexterity Saves

When a creature uses a melee attack to shove a creature and succeeds, they force that creature to move to another String as if that creature used the 'Skip' movement option. When a creature succeeds on a Dexterity saving throw, it must move to another String as if it used the 'Skip' movement option. If there is no free space for the creature to jump to, it automatically fails its Dexterity saving throw.

Areas of Effect

All Areas of Effect are changed to extend an infinite distance along the caster's current String. All AoEs centered on the caster or effects similar to such (e.g. the thunderwave spell or a Paladin's Aura of Protection) extend in both directions along the String, while any other AoE (such as the fireball or lightning bolt spell) extend in a single direction of the caster's choosing.

Ranged Attacks

Creatures do not suffer disadvantage for attacking an adjacent creature with a ranged weapon. You cannot shoot "through" a creature with a ranged attack, and can only attack creatures on your current string.

Flanking

While a creature is "surrounded" (the two spaces on either side of it are occupied by hostile creatures), it grants advantage to all attack rolls made against it.

Opportunity Attacks

When a creature uses one of its Moves to Slide or Skip, a hostile creature in an adjacent space may first make an opportunity attack. A creature that uses a Move to Swap does not trigger an opportunity attack from the creature it is swapping with, but a hostile creature in the other space adjacent to it when it Swaps may make an opportunity attack before it Swaps.