Whenever that creature deals combat damage to a player or planeswalker this turn, draw that many cards
Undead Alchemist is a fun one to create token, which you can tap for more mill

Historic Agent of Treachery Ajani, Nacatl Pariah Ancient Tomb Arid Mesa Armageddon Blood Moon Bloodstained Mire Brainstorm Broadside Bombardiers Channel Chrome Mox Commandeer Crop Rotation Dark Depths Dark Ritual Daze Demonic Tutor Devoted Druid Eldrazi Temple Entomb Field of the Dead Fireblast Flare of Cultivation Flare of Denial Flare of Duplication Flare of Fortitude Flare of Malice Flooded Strand Food Chain Force of Will Frantic Search Fury Grief Harbinger of the Seas Intruder Alarm Land Tax Library of Alexandria Lightning Bolt Mana Drain Marsh Flats Memory Lapse Mishra's Bauble Misty Rainforest Mox Opal Mystical Tutor Natural Order Necropotence Nexus of Fate Oko, Thief of Crowns Once Upon a Time Painter's Servant Polluted Delta Preordain Pyrokinesis Ragavan, Nimble Pilferer Reanimate Scalding Tarn Scholar of the Lost Trove Seething Song Show and Tell Sneak Attack Solitude Spreading Seas Strip Mine Subtlety Swords to Plowshares Temporal Manipulation Thassa's Oracle Tibalt's Trickery Time Warp Uro, Titan of Nature's Wrath Vampiric Tutor Veil of Summer Verdant Catacombs Wilderness Reclamation Windswept Heath Winter Moon Wooded Foothills Many cards banned in Pioneer are also banned in Arena's Historic format, though some, like Winota, Joiner of Forces, are notably absent from Historic's ban list due to the format having a wider range of responses for it

They need to make a profit reselling the cards, so youre paying for the convenience of instant payment
There are other cards like Councils Judgment and Assassins Trophy that have a similar effect
You cant go wrong with either, but The Great Henge is generally the better of the two, and it's one of the best creaturefall cards if you plan on playing creature-heavy green decks