Rune Dragon (Ancient, Spellcaster)

Magic Sense. The rune dragon is aware of any active magical abilities and effects within the listed range. When the dragon Seeks, it gains the benefits of a 4th-rank detect magic spell within the listed range (in addition to the normal benefits of Seeking).

Runic Scales. The rune dragon's scales function as runestones. The rune dragon can't use the effects or abilities of the runes etched on its scales, but they can transfer these runes to appropriate objects. Transferring a rune to or from an item in this way requires 1 minute, during which the dragon is . The process is automatic and doesn't require a check, but if the dragon stops or is interrupted in this process, the rune is destroyed. A rune dragon can have any number of runes etched on its scales, though they typically have only a handful of runes etched on their scales at a time.

Canceling Rune. Trigger The dragon is the target of a spell that requires a saving throw
Effect The dragon attempts to unmake the spell's foundational runes. They attempt to counteract the spell (counteract rank 10th, counteract modifier {+33}). If successful, the dragon is unaffected by the spell; other subjects are affected by the spell normally. The dragon can't use Canceling Rune again for {1d4 rounds}.

Retributive Rune. Trigger A creature within 15 feet damages the rune dragon
Effect With a burst of runic magic, the rune dragon uses their detonating rune ability on the triggering creature and immediately causes the rune to detonate if it didn't automatically do so.

Detonating Rune. The rune dragon's Strikes and abilities can leave a detonating rune on their targets. If a creature would receive a detonating rune while they already have one, instead of adding another rune, their current detonating rune activates, dealing 6d6[untyped] damage to the target and expending the rune. The detonating rune's damage type matches the dragon's current Shifting Rune. A creature can use an Interact action to remove the rune. Detonating runes fade after 1 minute if not detonated.

Entangling Rune. The rune dragon creates a large trapping rune in a within 60 feet. A creature other than the dragon that enters a trapped area or ends their turn in the trapped area activates the rune, causing it to entangle them. That creature must succeed at a save or become for 1 minute or until it Escapes. The rune can trap only a single creature at a time. The rune vanishes either when a creature succeeds against the rune, when a creature successfully Escapes the rune, or after 1 minute. A creature adjacent to the rune can use an Interact action to remove the rune.

Runic Breath. The dragon launches hundreds of exploding runes that detonate upon impact, dealing 17d6[untyped|options:area-damage] damage in a ( save). The damage type of this ability is determined by Shifting Rune. Creatures who fail the save are also affected by detonating rune. The dragon can't use Runic Breath again for {1d4 rounds}.

Shifting Runes. The rune dragon chooses between acid, cold, electricity, fire, or sonic damage. The runes etched upon the dragon shift, forming runes of that energy on its scales. The dragon gains immunity to that damage type, and their detonating runes and Runic Breath deal that damage type. Anyone trained in Arcana can immediately recognize the energy type of the etched rune without a check.

Trail of Runes. The rune dragon Strides, leaving behind a collection of runes wherever it steps. The dragon chooses to leave behind either detonating runes or entangling runes. Every space that the dragon moves through, including spaces occupied by creatures, gains a rune. These runes automatically activate when a creature other than the rune dragon enters the space or ends its turn in the space. The runes can otherwise be removed or vanish like normal.