Well, let's see. Very descriptive description of the physical features of the barrow, no need for a map here as it seemed quite clear in my mind's eye. Thank you.
Would this be somewhat contrived and party disrupting if a large group encountered them? Most definitely. However, this would be pretty cool for an individual or pair of players interacting.
I think I would break these up and scatter them across the forest, and also allow that some of them have been looted already.
So there, likely useful for all of us.
Interesting setup. Forcing the players to stand alone like this could provide for some good gameplay, but I would still probably tweak it a bit to give my players the option of seeking more help. Perhaps the barrier could allow a second player (or third) through if the subject of the test requested it? There should be a significant penalty or other alteration to the test to make the first player hesitate to do this, however. I would probably also remove the barrier against sound entirely, so that the rest of the party can at least stand by and shout advice, thus remaining more involved.
A few other small nitpicks: challenges one and two (judging the baby case and dealing with the live baby) are significantly easier than the rest of them, and might cause a party to cry foul when faced with the later challenges. Also, you forgot to include the answers to the three riddles.
Overall though, well done.
Overall, I like this. The puzzles are interesting and practical and I think there is enough description to carry it through.
I probably wouldn't use it myself. While I see the challenge in making a single player face a barrow alone (and I would applaud a GM who could pull it off), I don't like the idea of making the rest of the players wait around. The few times I've ever done something like this, I've lost control of the group (players would lose interest, get up and wander around, and have trouble getting back into play.) Maybe that says more about my limitations as a GM, but I have more success when I keep as many players involved as possible. Plus, I like seeing how a group responds to a challenge. That kind of group energy is the reason I play so few video games (and I'm too set in my ways to try those new-fangled MMORPGS.)
While I could be wrong, I think Echo's point is that this feels a little contrived. Your point about the classic dungeon being far more unrealistic and contrived is a good one that I fully agree with, which is why I don't run them.
I do prefer subs with some extra prose. Even though I would never read stuff like that off to the players, I find that that extra bit of flavor helps bring the ideas to life for me. I understand that that is a personal preference, so I don't knock off points for subs that don't do it. You provided enough detail to make it understandable and I commend you for that.
And bonus points for using barrow mounds. I've always been fascinated by them.
The plot hooks section is quite slim, especially with the mischief and outright disaster an anti-magic banner can wreak.
Also, I'd suggest adding some quirks and more personality a) to the known banners b) to the banners in general. So far, they're indestructible anti-magic banners. Woo.
It's okay, I guess.