Red

Fewer than a dozen Red worlds are charted, and surveys of the same world disagree. The Covenant reads a Red world as a place where the Prime Plane has worn thin against the Plane of Khaos or the Nine Hells. The Halcyion survey reads it as a Sentient world that died and has not finished. By assay the ocean is blood, and it is warm. Its current runs against the tide, and it clots around a hull that has been in it long enough.

Planetary environment

Crossing it

Navigate: DC 18
Forage: DC 20
Notice: DC 16

The current runs against the tide and changes without any cause the chart records. Samples taken from the sea spoil within a day.

Exposure

Rift Flux

Ambient Rift Energy at a high, unstable density, where channeling is stronger and less reliable.

WIS save, DC 13. End of each hour. Your next spell attack roll has disadvantage, or the target of your next spell that forces a saving throw has advantage on it. Roll once on the Surge Table.
- Dense field
  
  A spell cast here that deals damage or restores hit points adds its level to one of its damage or healing rolls, and a cantrip adds 1. A spell that does neither gains nothing. The bonus cannot be declined.
- Unstable
  
  A natural 1 or 2 on a spell attack roll, a target's natural 19 or 20 on a saving throw against a spell, and any failed concentration save each roll on the Surge Table in the GM's Manual.
- Instruments
  
  Anything calibrated against a stable Rift background reads wrong. Navigation, dating and detection checks that rely on one have disadvantage.
- Warded
  
  A ward, a null field or a feature naming Rift density removes the save and the Surge rolls. The damage and healing bonus goes with them.
Contaminated Atmosphere

Air that can be breathed and should not be: spore, ash, chlorine, coolant or fallout.

CON save, DC 12. End of each minute. The Poisoned condition until an hour after leaving the atmosphere.
- Filtration
  
  A rebreather or sealed suit removes the check. A filter mask gives advantage on it.
- Visibility
  
  Ash and dense spore make the area heavily obscured beyond Close range, in addition to their other effects.
- Radiological
  
  Where the contaminant is radiological, a failed save also inflicts a level of exhaustion that a long rest will not clear. It is removed by a Medicine check against the same DC, a restorative spell or a course of antiradiation drugs.
- Conversion
  
  A failure in Bloom atmosphere also counts as one day of exposure toward conversion.

In play

Sanguine Sea

Necrotic damage dealt on or in the ocean is increased by half, and radiant damage is halved.
Fear

A creature that spends an hour in contact with the sea makes a DC 15 Wisdom save. On a failure it is Frightened until it leaves the water and cannot be calmed by any means while it remains in the water.
Rift Flux

The Rift Flux environment applies across the whole world. In addition, a creature that fails a concentration save here rolls twice on the Surge Table instead of once and applies both results.
Spoilage

Samples from the sea clot and spoil within a day. Every account of a Red world is unverified, and no two agree.

Regions on it

Open Ocean Water with no bottom in reach and no cover of any kind, lit at the top and twilight below.
The Deep The water below the last light: cold, black, and the largest habitat on any water world.