@FxStarLight mutations are considered seperate monsters. Actual varients are rare monsters that only appear under specific conditions and can also only be collected once. My comment was about level farming, something commonly done in video games to overcome seemingly impossible difficulty jumps. That is impossible in this game/world except for the first to open a floor, as it's the only repeatable way to gain additional exp. Even with this, though, the amount of stats gained from level ups is pitiful compared to an essence. Where a level can be somewhere between 5-10, a single essence can be 20-50 with a special ability. This is why if someone forced a bad essence on you, you'd kill them -_-;
...because ✨MAGIC✨