Trailblazer

You touch one creature, causing flammable liquid to ooze from their pores when they move, which drips onto the ground before spontaneously combusting. For the duration of the spell, the following effects apply to the affected creature:

• They feel comfortably warm regardless of the ambient temperature.
• Their speed increases by 20 feet.
• Whenever they exit a space, they leave behind a trail of fire, filling a 5-foot cube in that space. This fire remains until the end of the affected creature's next turn, at which point it is extinguished. Up to 10 spaces can be set alight in this way at the same time. Beyond this number, each new space set ablaze extinguishes the oldest one. This fire is mundane and - at the DM's discretion - can be extinguished by other means. The fire ignites flammable objects in its area that aren’t being worn or carried. When a creature moves into the fire for the first time on a turn or ends its turn there, it must make a Dexterity saving throw. On a failed save, a creature takes 3d6 fire damage, or half as much damage on a successful save.
• Whenever they appear in a space via a teleportation effect (such as Misty Step or Dimension Door), a fiery explosion detonates in a 5-foot radius around them. Each creature caught in the blast (other than the recipient of this spell), must make a Dexterity saving throw. On a failed save, a creature takes 2d6 fire damage.

When the spell ends, the effects on the targeted creature cease, but any remaining fires persist until extinguished. Additionally, the targeted creature gains vulnerability to fire and cold damage until the end of their next turn, as their body temperature adjusts and returns to normal.