What the Hel?
The poor Vikings lead a faithful life, just as the gods demanded and now they stand in front of Asgard's gates to enter Valhalla. They always fought boldly, relentlessly pillaged Paris and Europe's towns, heroically stood against their enemies... And now this! The gods won't grant them what they deserve! They just shut the door right in front of them!
No Feasts, no mead, no roasted boar! No eternal glory or wild sprees by Odin's side. This shall not stand! How dare those ungrateful deities to abandon faithful Vikings just like that!
You won't get away with something like this when you deal with Vikings! Exiled and fallen from grace (and heavens), the Norse men get back on their feet and try once again to reach the realm of the gods and eventually earn their seat in Odin's halls!
High, on the peak of the very mountain they are standing before, they see a magic gate. Behind that, there must be Bifrost, the rainbow bridge, the door to Valhalla! If an honorable death is not enough to get in, probably just marching straight up into Valhalla does the trick!