Wander over to Brulosophy and take a look at their Hop Chronicles. They did some very interesting studies with various hop varietals and perceived aromas and flavor profiles...including magnum. It's very useful information to consider when looking to build a hop profile for your brews. Personally, I've benefited significantly from their work with hops, experiments, techniques, etc and is one of my "go to" resources. Give it a shot.
Regarding magnum, my takeaway from the hop chronicles eval is that the flavor/aroma profile imparted by magnum hops as a late addition are fleeting and not substantive enough for hoppier beer types and it's wise to rely on other hops to work with the magnum characteristics.