This in a way gives you nearly limitless number of opportunities to try and try again what you did, till you get the items you need. It is possible to save just before opening chests, trading with vendors or killing bosses. It is essentially taking advantage of the game's random loot generator system using saved games. Legendary Item Farming in Divinity Original Sin Enhanced Edition is known by various other names such as 'save-scumming' or 'Loot Farming'.