The Cloudultra 2 is On's trail shoe for long days. Max cushioning in a Helion superfoam midsole, a redesigned outsole with more ground contact, and a 5 mm drop that keeps you low and stable over rough ground. There is no plate. The knitted upper and the FlipRelease lacing exist for feet that swell over hours.
It suits you on ultra distances, and on any trail run long enough that impact rather than grip is what finishes you. At 295 g it carries its protection honestly.
It is not a light, nimble mountain shoe, and it is not a road trainer. If your trail runs are short and fast you will find it soft and slow, and the outsole is wasted on tarmac.