Vedalken is a blue creature type used for cards that depict a tall, thin, hairless blue-skinned humanoid race, with a dispassionate view towards life.  Their infatuation with knowledge makes these hyper-intellectual people natural Artificers and Mages. 
As of Mirrodin in 2003 merfolk were phased out as the iconic blue race, because of their limited suitability away from a water environment. This (not coincidentally) coincided with the rise of the cunning—and leg-having—vedalken. The vedalken loomed large throughout Mirrodin and Ravnica blocks, doing all the things that the other colors’ humanoids could do visually and narratively speaking, thanks to those feet of theirs. Then in Kamigawa block, where vedalken wouldn’t have felt very natural, the new soratami (Moonfolk) race appeared, also having legs while embracing blue-aligned flavor. 
On Mirrodin, the mycosynth created a vapor which induced mutations in the vedalken, who developed four arms and gills. Soon, this variation became the norm. These vedalken are physically very different from the members of their race found on the plane of Ravnica, and have more inhuman features, in some cases lacking a nose or visible ears. The center of their culture was the city of Lumengrid. 
Notable Mirrodin vedalken:
The vedalken of Ravnica are associated most closely with the Simic Combine and Azorius Senate. They look very much like tall humans, but with blue skin and little emotion.  Though the vedalken of Ravnica are physically different from those Mirrodin, some Simic biomancy experiments have produced similar results, including four arms and gills.
Notable Ravnican vedalken:
- Simic doctors Nebun, Zlovol, and Otrovac
- Azorius senators Illindivossk, Yindervac, Pollotorus, Natt Vinloskarga
- Modar Bejiri
Vedalken of Esper look very similar to their counterparts on Ravnica, but are more spindly, with elongated skulls. The vedalken, like all creatures in Esper, are enhanced by filigree of the mystical living metal etherium. The vedalken are among Esper's most prestigious mortal inhabitants and often hold positions of power thanks to their prodigious intellect and talent for spellcasting.
After Alara was reborn, some vedalken heretics from Esper were drawn to the verdant jungle of Naya. There they rejected the cold clutch of etherium in favor of the warm embrace of nature, seeking enlightenment in the infinite patterns of life rather than the dusty confines of ancient tomes. 
- Doug Beyer. (August 10, 2011.) "Magic's Exclusive Creatures", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Doug Beyer. (December 24, 2008.) "How to Design a Hellion and More!", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Doug Beyer. (June 25, 2008.) "Merfolk Resurfaced", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Doug Beyer. (December 08, 2010.) "The Nonhuman Cultures of Mirrodin", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Monty Ashley. (July 04, 2012.) "Sketches: Vedalken Entrancer", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Magic Arcana. (May 30, 2006.) "A Mutant Vedalken in Ravnica", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Magic Arcana. (April 30, 2009.) "A Vedalken in Alara", Daily MTG, magicthegathering.com, Wizards of the Coast.