Legion Casein+ is the grass-fed, naturally-sweetened option for someone who wants a clean premium label without going fully unflavored. It serves up 26 g of micellar casein — one of the higher per-serving doses in this lineup — from Truly Grass-Fed dairy, sweetened with stevia and free of artificial dyes, sweeteners and fillers, with the kind of fully-disclosed label Legion is known for. The downsides are price-related: it costs more per serving and gives you fewer servings per tub than the value leaders, and unlike the Ascent and NOW picks it doesn't carry an Informed Sport or NSF seal.
The brand cites its own lab testing, but that's a manufacturer signal, not an independent certification. If grass-fed sourcing and natural sweetening in a flavored casein are what you're after, it's a strong choice.