Him and his support are all pretty cheap
They're reskinned versions, with the same rules text, but in-universe MTG art and names
You need fewer cards in the graveyard per activation (albeit more specific cards), it has the same activation cost, it will typically deal more than two damage per activation, it will get larger over time, and it has menace
The extreme scarcity, combined with the prestige of owning a card signed by the author, has driven its valuation to insane heights
Showcase foil: $15 Borderless foil: $18 Prerelease foil: $16 Regular: $6.50 Urabrask, Heretic Praetor Another Phyrexian Praetor slipped into a Standard-legal MTG set, with the foil Phyrexian version of Urabrask, Heretic Praetor priced at around $45
Experimental Frenzy can provide Mono-Red Aggro decks with an unheard of amount of card advantage, which is extremely scary for an opposing deck thats simply trying to stabilize