Volcanic Veins

Characters with Volcanic Veins have a form of biological Tron Lines where their veins and arteries will glow intensely from underneath the skin, sometimes even "pulsing" in tune with their heartbeat or as if they had real magma flows inside their bodies. It should come as no surprise when dealing with characters who are elemental embodiments of fire and lava -- where it gets interesting is that this can be used for just about any biology and power set. Ice powers? Neon blue jagged veins. Ability to manipulate Pure Energy or Mana? Holy white veins. Control over poisons? Sickly green veins (which you probably really don't want to bleed on you). A Black Magic master who's Drunk On the Dark Side? Malevolent purple veins.

Thanks to Psychoactive Powers the veins will glow proportionally strong to the characters health and emotional state. Much like Eye Lights Out, if the character dies you can expect their Volcanic Veins to "dry up", darken, and maybe even harden like cooling lava. It should be noted that artists may not have done the research and draw Volcanic Veins over places or in directions normal surface veins don't go. Of course, it may be that a Wizard Did It and their "magical chi flow" doesn't necessarily have to be identical to their biological blood flow.

Compare Vein O Vision and X Ray Vision. Contrast Tainted Veins. See also Throat Light.

Comics -- Books

 * Both Finnegan and Gloriana in the Top Cow series Broken Trinity starring the Witchblade and The Darkness have Volcanic Veins. In Finnegan's case they're bright blue and ice power based. Gloriana has magma red veins.

Films -- Animation

 * Near the end of Atlantis the Lost Empire, after Rourke is transformed by the crystal's power, there are several bizarre glowing red veins visible all over his crystalized body.

Live-Action TV

 * Geordi was infected by a parasitic species in the Star Trek the Next Generation episode "Identity Crisis". Those infected turned into invisible aliens that could only be seen under UV light. When exposed, they had neon blue veins.
 * Used in a One Thousand Ways to Die anecdote about a rave attendee who got so wasted that he tried to mainline the luminous fluid from a glowstick. Justified in the anatomical animations, although the fluid's light probably shouldn't have been visible through his skin in the live-action scene.

Tabletop Games

 * Genasi (D&D version 3 onwards) have glowing lines on their bodies, unique to them and a sign of whatever element they are manifesting.

Toys

 * Adam Power, Shaya, and the Trigore from the Power Lords line of action figures.

Video Games

 * The PC's tattoos start doing this in the Fable series if you use magic often.
 * The boss Fyrus in The Legend of Zelda: Twilight Princess.
 * In Bio Shock this trope is invoked on the protagonist's veins quite frequently, depending on the plasmid at the time. It's suprisingly well researched too.
 * Groudon, Kyogre, and Rayquaza in Pokémon, with their veins prominently pulsating in the title screens of Pokémon Ruby and Sapphire/Emerald versions. Groudon manifests the "volcanic" part a bit more, since it rules over land and lives in a volcano.
 * The TzHaar in Runescape.
 * In Batman Arkham Asylum, Bane and the Titan Henchmen have glowing green Venom/Titan pulsating throughout their bodies.
 * Anders in Dragon Age II manifests these and Glowing Eyes of Doom whenever Justice/Vengeance asserts itself.
 * The Drakes from Battle for Wesnoth normally have green scaled skin, but the Burner family, with their stronger connection to their inner fire, have gray skin. As their fire gets stronger, it shows more and more through their scales and their veins that they eventually become blazing red, as in the case of Inferno and Armageddon Drakes.
 * Nano-soldiers in Red Faction 2 have either Volcanic Veins or Tron Lines around their eyes and down their arms that pulse when they do something nano-related.
 * The protagonist of Overlord II has bright blue veins on his dark blue skin.

Western Animation

 * In the latest episodes of Code Lyoko, the Kolossus sports quite literal Volcanic Veins since it has the appearance of a giant lava Golem. As expected, they cool down and the glow light off once it's finally killed.
 * From Wakfu, Rubilax the major Shushu also has glowing Volcanic Veins in his true, demonic giant form.
 * Megatron from Transformers Prime briefly displays Volcanic Veins as a result of being corrupted by Dark Energon during his fight with Optimus Prime.