They rushed forward to meet the large sahuagin. They had been chasing its partner for almost a mile overland, and were not about to lose it now just because the scaly monster dove beneath the surface. It had taking the jade statue, and Thia’s Troublefinders had sworn to the Deacon Thadeous that they would retrieve the statue. As they began to tread water towards the four-armed fish-man, they glimpsed movement below. It was a trap, and they had blundered right into it!
This is the fourth in a series of blogs, designed to help you add a little moistness to your 4e D&D game. The first half of this blog provides a few examples of layers, with rules for those provided in the previous entry of this series.
Sample Layers
Below are a few samples of how a layered encounter map might be designed.
Shoreline
This is a simple three-layer encounter location.
The top layer of these maps includes a large beach along the side of the map and increasingly deep water along the other half. The 3 squares closest to the beach are difficult terrain and do not require Athletics checks, but creatures cannot move between layers in those squares. Additionally, creatures on other layers have total cover from creatures on the shore.
As characters move farther away from the shore they begin to swim, and start making Athletics checks when they are 4 squares from the beach. Once they are swimming they can move between layers and can target creatures on other layers normally.
The second layer is smaller than the first, with a steep slope on the far right squares. Creatures in a sloped square do not sink when they fail Athletics checks. This layer is close to the sandy beach, and the movement of combat is disturbing the sediment. All squares in this layer are considered to be lightly obscured.
The third layer is only slightly smaller than the second. The water on this clear and offers no concealment. Along the side runs the rocky shore, now a vertical drop.
This third layer can be modified with such features as small underwater cave. Other layers could include terrain such as coral or seaweed.
Iceberg
This is a very simple four layer encounter
The top layer is the surface of the water, with a small iceberg exposed on the surface, along with other floating chunks of ice.
The iceberg is solid but only partially above the water, so it provides cover (but not superior cover). Moving from the water onto the surface of the iceberg costs an extra square of movement. The iceberg itself has slippery icy patches. Creatures that move more than 3 squares must make a Moderate DC Acrobatics check or fall prone.
The lower three levels are similar, all underwater with the iceberg in the middle of the battlemap. The iceberg itself blocks movement and line of sight. The only variation between layers is the size of the iceberg.
The water around the iceberg is dangerously cold. Creatures that start their turn adjacent to the iceberg take 3 cold damage per tier.
At the DM’s discretion, the iceberg could be clear in places, and thus would not block line of sight.
The iceberg could also move as the fight progresses, acting and shifting cover. If a moving iceberg strikes a stationary character they must make an immediate saving throw. If they succeed they remain on their current layer but are pushed along by the iceberg. If they fail, they are pushed down a layer.
Whirlpool
This is a more complicated four-layer encounter location.
The top layer of this map is the surface of the sea. Dominating the middle of the layer is the opening of a vortex, sucking creatures underwater.
On this layer the whirlpool is burst 5 zone, 11 squares across. Creatures that end their turn on the outer 3 squares are pulled 1 square closer to the center of the zone and slide 2 squares clockwise. Creatures that end their turn on the inner squares are pulled down a layer.
On the second layer, the whirlpool is a burst 3 zone, 7 squares across. Creatures that end their turn on the outer 2 squares are pulled 1 square closer to the center of the zone and slide 2 squares clockwise. Creatures that end their turn on the inner squares are pulled down a layer.
On the third layer, the whirlpool is a burst 1 zone, 3 squares across. Creatures that end their turn on the outer squares are pulled 1 square closer to the center of the zone and slide 1 square clockwise. Creatures that end their turn on the inner square are pulled down a layer.
On the fourth and lowest layer, the whirlpool occupies a single square; the whirlpool does not move creatures but counts as difficult terrain.
Sample Encounter
This uses the shoreline maps. That map can easily be cropped to three wide but short battlemaps, each covering a narrow section of the shoreline.
(This encounter does use monsters from the MM1, so remember to increase their damage before use.)
Encounter Level 9 (2002 XP)
Setup
4 sahuagin guards
1 sahuagin raider
2 sahuagin priests
1 sahuagin baron
The fight starts with the sahuagin baron on the first layer, swimming but visible. The remaining sahuagin begin the fight underwater: the guards and raider on the second layer, and the two priests are on the third layer.
Tactics
The baron swims out to open water where it can use its swim speed to greater advantage, goading the PCs to come and attack. Meanwhile, the raider and guards will await below, possibly throwing their tridents to strike the PCs, and acting as living cover for the priests.
The sahuagin, knowing they will be fighting at a distance, should have brought a spare trident. The tridents also likely sink, allowing missed projectiles to be recovered as the slowly descend.
Once the PCs are in the deep water, the baron will swim down, and join its allies on the second layer.
Features of the Area
Sediment: The sand stirred-up on the second layer, and grants concealment to targets on different layers.
Terrain
Under the waves there are dangers unknown on the surface, areas of unique wildlife and locations of power.
Under the waves there are dangers unknown on the surface, areas of unique wildlife and locations of power.
Dark Water
This is an area where the foulness of the shadow realm has tainted the waters, turning them black and foul. The water is sticky and thick, making swimming a challenge.
Effect: Squares of dark water are lightly obscured and creatures with a swim speed treat the area as difficult terrain. Creatures without a swim speed take a -5 penalty of Athletics checks.
Fey Algae
Infused by the living force of the arcane world of the Fey, this resembles pond scum only much more virulent and found in any aquatic environment. It forms thick clouds that blocks vision and clings to anything that enters.
Effect: Squares of fey algae are heavily obscured. Creatures that enter or start their turn in a square of fey algae take a -5 penalty to Perception and Stealth checks and a -2 penalty to attack rolls (save ends).
Geyser Jet
Similar to a thermal vent, these periodically erupt in a torrent of scalding water.
Effect: The DM rolls a d20 at the start of each round. If the result is 9 or less the geyser erupts; creatures in burst 1 around the geyser take 5 fire and acid damage per tier.
Jelly Bloom
These are massive schools of jellyfish, sometimes thousands of the creatures, which float through the water and act as a hazard to swimmers.
Effect: Creatures that enter or start their turn in a square of a jelly bloom takes 10 lightning and poison damage per tier.
Razor Coral
This sharp-edged coral seems harmless but is sharper than polished steel.
Effect: Creatures that enter or start their turn in a square of razor coral take ongoing 3 damage per tier (save ends).
Tangle Weeds
Patches of this seaweed have been known to drown divers and snare the unwary.
Effect: Creatures that enter a square of tangle weed must make a Moderate DC Athletics or Acrobatics check or be grabbed (until escape). The escape check uses the same DC, but with a -2 penalty on the check.
Thermal Vent
These chasms send out waves of heat, and legends say they are clefts into fiery regions of the elemental realm.
Effect: When a creature enters a square with a thermal vent they take 5 fire damage per tier and the creature is pushed up 5 squares.
If the encounter takes place on a layered battlefield the creature is instead pushed up a layer.
Undertow
A side effects of powerful waves, this is an underwater current that pulls people down into deeper and deeper water.
Effect: When a creature enters an undertow they must make a moderate DC Athletics check or be pushed down 5 squares.
If the encounter takes place on a layered battlefield the creature is instead pushed down a layer.
Similar Posts:
- Aquatic Adventures III: Rules
- 4e and the Art of the Limit-Break: Divine Limit Breaks
- Aquatic Adventures II: Encounters
David aka Jester has contributed to the Powersource Podcast, Goodman Game's "Book of Rituals", "Dragon" magazine, and has been a longtime member of the Ravenloft fan-community the "Fraternity of Shadows". His semi-regular blog can be read on the Wizards of the Coast community site. Follow him on Twitter at: twitter.com/DnDJester 
Awesome. This is really awesome. Thanks!
I got a paizo flipmat, which is divided into thirds. Each third is a variation on theme. One third is a boat pulled on shore, one is the boat wrecked on shore, and the final third is the boat sunken on shore. I recommend it to anyone running aquatic, or pirate themed campaigns.