I purchased the base game of War Chest on a whim as someone who loves strategy games, but finds Chess too... simple. The strategic situations Chess brings up are never really that interesting, and with enough study, there seems to always be one right move. War Chest breaks that with its very well implemented luck, creating varied situations and battles that seem to evolve over time.
War Chest: Nobility takes what's good about War Chest and adds more! Where in the base game, the Royal Coin always felt kind of bad to draw, in Nobility, it's exciting, as it's that coin that brings into play the new Decree cards, which can shift a battle super fast if your opponent isn't paying attention. These cards create more "ahah!" moments, which is what made me love the base game in the first place.
And I haven't even talked about the new units! (They're good, and work well with the base units. None of them feel like they're too different or weird.)