That slot initially was Ashen Rider, but a lot of the decks that play Karakas (Lands, Death and Taxes) also produce other troublesome cards like Oko, Thief of Crowns, or just multiple copies of Karakas
Whether you dominate the battlefield with lifedrain, control your enemies with sheer cunning, or summon an army of the undead, these vampire card sleeves bring an aura of elegance and menace to your deck
Even without other synergies, hes somewhat broken mechanically: bare minimum, Vivis ability should have been a tap ability to begin with
The tapped entry is a serious downside here because mono-white decks usually play a low curve, and its a major hindrance if you fail to play a mana rock or a turn-1 creature beacuse this is your only white source
This means that some non-Oko strategies will face dedicated opposition for the first time