Its not legal in any format, but for collectors its a piece of Magic history regardless, forming part of the Power 9 (more on those shortly)
Color identities are back too, such as Zuko kicking off as red then into red, white, and black to represent Mardu, which will be a legendary hero
Endpoints (especially for card data) have specific hard rate limits
Im not sure why, but Quasiduplicate is templated as choosing a target and this just copies a creature on resolution, so your opponent can counter Quasiduplicate with a removal spell, but if you have multiple creatures on the battlefield, theyd need to kill all of them to counter this, which actually makes it a lot safer to use in Constructed Magic
On attack, Narset, Enlightened Master lets you exile the top four cards of your library and play any non-creature spells (instants and sorceries) without paying their mana costs