UBG Living End is a cascade combo deck that uses Violent Outburst and Shardless Agent to cast Living End for free, resetting the board with a graveyard full of large cycling threats like Striped Riverwinder, Curator of Mysteries, and Architects of Will. Grafdigger's Cage is your most important sideboard card here — it completely prevents Living End from functioning since it stops creatures from entering the battlefield from the graveyard. Hexing Squelcher applies early pressure and disrupts their cascade spells by forcing them to pay more mana, which can break the free-spell angle entirely if they can't cast Violent Outburst on curve. Pyroblast answers Force of Will and Force of Negation, clearing the way for your combo pieces. Cut Sneak Attack since it's a three-mana investment in a race where they can reset the board and undo your setup, and cut Prismari Charm and Spell Pierce for your more impactful hate pieces.