I think the best places for a planeswalker are in midrange and control decks, since their main strength lies in gaining incremental advantages over the course of a game
At the beginning of each opponent's upkeep, that player sacrifices a creature of their choice.
In my cube particularly it is not all that uncommon for this to have no targets and most of the time it will only have a couple
References Wizards of the Coast, Duskmourn: House of Horror Release Notes Wizards of the Coast, Gatherer Card Database: Zimone, Mystery Unraveler Scryfall, Manifest Dread card search Scryfall, Growing Dread Scryfall, Threats Around Every Corner Scryfall, Vannifar, Evolved Enigma Draftsim, Manifest and Manifest Dread in MTG: Rules, History, and FAQ Draftsim, The Best Manifest and Manifest Dread Cards in Magic Ranked Wizards of the Coast, On Proxies, Policy, and Communication