Plus, for a rundown of all the cards across the set and where you can find them, check out the Collecting Dominaria United article, which includes details on the Lost Legends cards
This card is so good that its banned in Modern, Pauper, and Legacy
For three mana, you can tap Feldon to create a token of a Creature card in your graveyard, except its also an Artifact on top of other types
The book side is sometimes relevant, especially when converting to your janky infinite mana and storm wins via Hullbreaker Horror and Jadzi, Oracle of Arcaivos, but in my experience, youre more interested in bouncing the book back to your hand than actually using it
At its best, though, playing a couple of these in a row will allow you to become essentially unbeatable very quickly
A common card is usually worth only a few cents, while a rare or holographic card can be worth hundreds of dollars