# Blue Dragon ## Regional effects _Source: Monster Manual (2024)_ The region containing an adult or ancient blue dragon's lair is changed by its presence, creating the following effects: - **Sinkholes.** Sinkholes form more frequently in the area within 1 mile of the lair. Whenever a creature in that area other than the dragon and its allies finishes a [Long Rest](3-Mechanics/CLI/rules/variant-rules/long-rest-xphb.md), roll `d20`. On a 1, a sinkhole opens beneath the creature, and the creature must succeed on a DC 15 Dexterity saving throw or fall `2d4 × 10` feet into the sinkhole. - **Spiteful Storms.** Dust devils and thunderstorms rage within 1 mile of the lair. The area is [Lightly Obscured](3-Mechanics/CLI/rules/variant-rules/lightly-obscured-xphb.md). If the dragon dies or moves its lair elsewhere, these effects end immediately.