Glacial Moon

When the frozen celestial body ascends to its place in the night sky, it conjures forth the very essence of winter, blanketing the world with an unyielding blizzard that saps warmth from bones and clarity from thoughts. Few dare to brave the frigid streets during this time, for the perils that lurk in the shadows are as merciless as the cold itself.
When the Glacial Moon is visible, the following effects apply to the world.

Monsters

Monsters gain resistance to cold damage; if they already have this resistance, they become immune to cold damage instead.

They gain temporary hit points equal to their CR when the moon first rises (minimum of 1).

If an undead creature is hit with a melee attack while they have these temporary hit points, the attacker takes cold damage equal to the initial number of temporary hit points.

Travel

The world is engulfed in a permanent blizzard that assaults the body and the mind and greatly limits visibility. Creatures other than monsters suffer a -10 penalty to Perception checks and their passive Perception scores. If they travel at a fast pace (as per the travel rules), they are considered blinded.
For each hour that passes, roll a d6. On a roll of 1, a strong blizzard wind rises. Each member of the party must succeed on a DC 14 Constitution saving throw or take cold damage equal to their level. In addition, whenever this blizzard rises, the party must succeed on a DC 16 Survival check or get lost. If they are lost, the group’s travel time increases by two hours.

Madness

The madness section of each moon refers to a Madness DC, which is indicated in the following table.

Average Party Level

Madness DC

1-4

11

5-8

13

9-12

15

13-16

17

17-20

19

21+

21

The cold paired with the madness slows the body. If a character gains a madness, be it short, long, or indefinite, they must make a Constitution saving throw against the Madness DC or gain one point of exhaustion. Characters with resistance or immunity to cold damage automatically succeed on this saving throw.

Short-Term

Whenever a character gains a short-term madness under the Glacial Moon, their body numbs and they suffer a -1d4 penalty to all attack rolls and saving throws until the madness ends.

Long-Term

Whenever a character gains a long-term madness under the Glacial Moon, they feel compelled to suffer the cold to cleanse their body. Whenever they are in extreme cold, to better feel the merciless bite of the cold against their skin, they remove all their clothing, save for their undergarments, and refuse to dress up. This weakens their body, giving them disadvantage on Constitution checks and Constitution saving throws while in the cold environment. Characters that are immune to cold damage do not suffer this effect.

Indefinite

A character that gains an indefinite madness under the Glacial Moon becomes numb to the world around them.

• Roll a d100;
• on a result of 33 or lower, the character’s body becomes completely numb to all sensations, and they add their proficiency bonus to any Concentration checks and to any check made to endure pain.
• On a result of 34 or higher, the character’s body suffers severe frostbite, numbing their nerves and body, crippling them. They have disadvantage on Dexterity checks and Dexterity saving throws, suffer disadvantage on all attack rolls made using Dexterity, and can’t add their Dexterity modifier to their Armor Class or initiative rolls. This eldritch frostbite can only be cured if the madness is removed.

Type

Metaphysical, Supernatural