Dire Winter 「True Dweomer」

9th-level Evocation (Druid, Sorcerer, Wizard)

• Casting Time: 1 minute or Circle Magic option
• Range: 1 mile
• Components: V, S, M (an intact blue dragon’s heart frozen in absolute zero liquid, and a continuous-melting icicle from the Elemental Plane of Ice, plus a separate offering of 100,000 gp, all of which the spell consumes)
• Duration: 1 day

You summon a howling frost centered on a point that you can see within range. A temporary sphere of supernatural winter erupts in a 1-mile radius, altering the region periodically as temperatures drop. The weather in this area becomes drastically altered, modifying Extreme Cold rules and related freezing environment effects. You exercise absolute control over the initial environmental factors of this area, determining its atmosphere, temperature, water availability, and general localized effects in the layout. In doing so, you can manifest any of the following conditions:

• Blizzard: Water vapor is instantly flash-frozen, producing a continuous, blinding blizzard. Sunlight is completely blocked out. Everything is Heavily Obscured beyond 30 feet (creatures more than 30 feet apart have the Blinded condition relative to each other). Creatures that rely on sight and hearing have Disadvantage on Wisdom (Perception) checks. Ranged weapon attacks have Disadvantage, and unprotected flames are instantly extinguished.
• Extreme Cold: A creature without cold-weather gear or Cold Resistance must succeed on a DC 10 Constitution saving throw with Disadvantage at the end of each hour or gain one level of Exhaustion.
• Freezing Aerial Mists: A creature that breathes deeply within the mist must succeed on a DC 10 Constitution saving throw or gain one level of Exhaustion.
• Frostburn Atmosphere: The ambient temperature drops to absolute zero at midnight. Any creature entering the area or starting its turn within 30 feet of it takes 7 (2d6) cold damage from flesh-shattering frostburn. This damage pierces cold resistance; immune creatures take half damage.
• Glacial Terrain: The area becomes permanent severe difficult terrain of slick ice and deep snow. Complex structures may fracture and collapse under internal ice expansion.
• Whiteout Navigation: Any creature leading a group through the blizzard must succeed on a DC 10 Wisdom (Survival) check at disadvantage every hour or the group becomes lost.

Additionally, you must succeed on a DC 45 Intelligence (Arcana) check to decipher the foundational science of high-magic spellcraft and anchor the new reality. On a failure, you suffer backlash as the spell automatically fails, you take 99 (18d10) psychic damage, the sphere disappears, and the material components are wasted. After this spell is cast, you gain 1 level of Exhaustion. This effect ignores resistance and immunity. While you have Exhaustion levels gained from this spell, finishing a Long Rest neither restores lost Hit Points nor reduces your Exhaustion level.

Casting this spell on the same spot every day for one month makes this effect permanent.

True Dweomer. Magic of high power automatically fails the very first time you cast this type of spell, requiring you to expend twice the amount of time and resources to effectively complete this magic of high power at least once. In doing so, and successfully casting a true dweomer spell, you attract instant cosmic scrutiny. The severe metaphysical friction of shaping this forbidden magic weakens your form. After casting this spell, each time you cast a spell until you finish a Long Rest, you take 1d10 necrotic damage per level of that spell. This damage ignores resistance and immunity. Furthermore, your Constitution score becomes 3 for 2d4 days while simultaneously your Intelligence score becomes 3 for one month. For each day you spend resting and doing nothing more than light activity, your remaining recovery time for your Constitution score decreases by 2 days. Finally, there is a 33 percent chance that you are unable to cast Dire Winter ever again.

Casting as a Circle Spell. Casting this as a Circle spell requires a minimum of five secondary casters, which reduces the casting time to 8 hours. Every caster gains 1 level of Exhaustion per participant (to a maximum of 4 levels from this rite). When the spell is cast, each secondary caster must expend a 8+ spell; otherwise, the spell fails.

The number of secondary casters determines the spell's area of effect and duration, as shown in the table below. The spell ends early if any caster who participated in this casting contributes to another casting of Dire Winter as a Circle spell.