The Lost Vikings update has been applied to the Heroes of the Storm closed beta.
This means Olaf, Baleog, and Erik are now available to play around with.
Olaf has lots of heath, regenerates it quickly and charges to slow enemies; Baleog deals splash damage to enemies behind his attack target; and Erik moves faster than the other fellas and has a longer attack range. ‘
Special moves for each Viking as well as other patch notes concerning the user interface, art, the shop, and other changes, can be found over on Battle.net.