The Elf is a wizard-class hero from the base set.
Elf Wizard (Level 1)
The Wizard has a Magical Attack of +2, and is a light source of 1.
Elf Sorcerer (Level 2)
The Sorcerer has a Magical Attack of +3, and is a light source of 2. Additionally, as a Spoils effect, he can remove a monster from the dungeon hall before restocking it.
Elf Archmage (Level 3)
The Archmage has a Magical Attack of +4, is a light source of 2, and can remove a monster from the dungeon hall as a Dungeon: ability, placing it under the dungeon deck. Additionally, it is worth 2 Victory Points.
Rulings and Errata
The Elf will likely be given the elf (type) keyword when AEG releases errata for Classic Thunderstone, but currently it is not an elf. However, there are currently no cards that trigger off the elf keyword, so that's okay.