UR Delver, or simply Delver, is an aggro deck that mimics the old "counter-burn" archetype. Delver uses very few creatures, usually only Delver of Secrets and Snapcaster Mage. Instead, it focuses on cheap burn spells and counterspells to transform a Delver of Secrets on turn 2 or 3, resulting in a very early 3/2 flying creature.
UR Delver is very straightforward, as its main goal is to kill its opponents as quickly as possible.
Here is a sample list: