First, the Trueheart Duelist is a 2/2 that takes 1 colorless and a White (1W) to cast. The Duelist can block an additional creature each combat. This is relevant because the Duelist can potentially trade with two creatures at once in combat. But the Duelist gets even better than this. The Embalm mechanic is where the beauty of this card comes in.
On his own, Trueheart Duelist looks like a really good creature, especially in draft. But with the Embalm ability, this seems like a Constructed-viable card, too.