(Im looking straight at you, $15 Thing in the Ice!) Sorin, Grim Nemesis I like that he lets you draw and punish all at the same time
Then you drop the hammer and go extra super mega slug
Sisus ability goes a bit further, though, because it allows you to choose which card you take, instead of throwing yourself completely at the mercy of a random draw
Ive heard some call it the green Shelly (Sheoldred, the Apocalypse) for formats like Standard and Modern and its not a perfect analog since Ouroboroid cant just solo people like Shelly can, and is worse against bolts but it does highlight something: letting this live for a turn or two can make life rough, even on its own
As mentioned, MTG Arena does offer in-game purchases of digital currency, which can then be spent on packs of cards
Razaketh is an evasive threat with both flying and trample, but its power lies in its activated ability that allows you to pay two life and sacrifice a creature to tutor for any card in your deck at instant speed