Strategies utilizing multiple permanent types in 1 or more engines with low CMC cogs are also quite viable and extremely dangerous even in environments with a reduced card pool
Like most Magic: The Gathering cards, the value of Xanathar, Guild Kingpin depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Adventures in the Forgotten Realms)
Before that it was in Commander 2014
Once its out, you get constant knowledge of your top card and the green light to cast creatures from there
If your Ratcatcher does not survive the turn cycle, you essentially spent six mana to get a removal spell out of your opponents hand, putting both players behind of the rest of the table
What makes Farewell to Arms one of the best cards in the history of the game is how it excels at breaking the opponents mouth, but also their body