Wheel of Fortune, Windfall, and Brainstorm are but a few of the common wheels (cards that cause everyone to discard their hand and redraw a full one) and low mana value card draw engines that get this swarm humming, and if you run out of quick card draw options, 4 mana will let you loot an extra card in your deck to try and find the next one
You can't make choices or decisions for that player that aren't called for by the game rules or by any cards, permanents, spells, abilities, and so on
While choosing targets as part of casting a spell or activating an ability, your opponents must choose at least one Flagbearer if able
Its a staple in black decks for a reason, and it fits Halloween like a bloodstained glove
My goal is not to fault you for playing those cards - I just feel the broader EDH format as a whole is becoming quite solved, in part by people turning to net-decking or using automatic online suggestion tools too often