While the core rules of Dungeons & Dragons 5e are perhaps the best official iteration of the game to date, the system is far from perfect. Oftentimes that's where homebrew DnD rules come in, allowing players to adjust their play experience to their liking. While homebrew can be used to modify the game to accommodate a particular genre of story or character concept, other homebrew rules are broader, implemented to fix larger issues within the rules of DnD 5e.

https://screenrant.com/dnd-homebrew-rules-5e-potions-flanking-blood-hunter/