The power that comes from devoting yourself entirely to ambition is huge amounts of mana through swamps matter cards such as Crypt Ghast and Cabal Coffers, as well as having no issue casting cards such as Grave Pact and Necropotence
If you have cards that benefit from banishing items on the field, well, now youre in business
If it has neither, create a Food token
The miracling Reforge the Soul was heavily played and very cheap on the market after printing, but with just one reprinting since then it's slowly risen in value over time, and now the Commander deck bulk rare that was never printed in a Standard legal set is massively cheaper by a whole 6 bucks
The CMC restriction ensures that he doesnt scale too well to Commander, and only triggering off of legends, artifacts and sagas means that its really hard to build around triggering his ability consistently while also having relevant creatures to return
For me, Belle is actually one of my favorite cards from The First Chapter from a playability standpoint at well, with two fantastic abilities