Its low cost makes it the perfect tool to handle aggressive decks that exploit cheap creatures or token producers like Gleeful Demolition
You can also choose not to find a card, even if there is a Wizard card in your library.
Withengar even has an ability that lends it to be used in multiplayer formats like Commander, as when another player loses the game, thirteen +1/+1 counters are put on the Demon
Still one of the top decks of the game, with OP5 he gains good cards, especially Amaru
If you want to catch up on the new cards and figure out what to grab for your decks, then our Commander Set Review for Foundations is right up your alley
The idea is to use Auras and Enchantments to get your foes fighting anyone but you, while still having some solid creatures to attack or defend when you need to