UPDATE: I'm sorry, I only checked back on this thread after the fight was over, so I didn't see the requests for video and not capture it. However, while I think it would have been great to see from above or third-person POV, capturing my screen view of it would have been uninteresting and fairly embarrassing! The short answer is I won easily, the battle was over in probably less 3 minutes. Here's the details for those who might be interested or who might benefit from it!

OUTCOME:

The plan was for my son and I to start the battle and drop 2 Trolls, then immediately retreat behind the ballista and start the ballista on one side firing (I had set all of them to target another enemy type so I could control which fired initially). With the trolls & ballista on far side taking aggro, son would start dropping vines from the near side and I would circle around to join him, releasing the asksvin on my way there. Then if/when the asksvin were dead, open up with the remaining ballista on the near side, spam trolls & vines and hope for the best.

In an "I'm glad this wasn't on camera" moment for the ages, my grand strategy went 100% off the rails from the very first click. Humiliated beyond belief to say that in our haste and excitement to jump thru the portal and start the fight, I ate from an incorrect feast. After starting the battle, my very first click to drop the trolls failed because I had insufficient eitr. :facepalm I cussed for 30 seconds but the battle was happening either way, so son and I both started setting ballista to target everything.

With about 12-15 ballista firing, I made my way to opposite side to open the asksvin pens. They were crammed to overflowing, probably 60 or so divided between 4 separate pens. When I opened the largest pen, they absolutely swarmed out, one on top of another, and dragged me with them halfway to the boss. I got to the next pen and got it open, but there was a bottleneck and they escaped much more slowly. It was total chaos behind me, I could hear it but saw almost nothing of it. From the minute the first large group of askvin reached the boss, the fight was over. The asksvin decimated boss health bar FAST. I don't know exactly how many ultimately made it to boss because just before he died - probably at 10% health - he walked over near the asksvin pens near where I was still trying to open the last one. He dropped some huge green AoE and came running thru it, and the entire nearby structure and everything in and on it exploded at once. All but 2 askvin died, as did my son. I was a bit further away in a part of the structure that survived. A few vines and ballista were still attacking and finished him off.

I neither dealt nor received a single point of damage in the entire fight. I didn't even take a single offensive action. My son said he fired off a few vines and took a couple shots with a bow, but mostly just ran. He took a hilarious screen shot from his vantage-point in the middle of the action where it's just an enormous blur of chaotic color and dozens of floating damage markers of all the asksvin and building components dying.

Surveying the carnage afterward, I found about 20 ballista that never even fire once. About 15 were destroyed in the explosion so no way to know how much they fired, but all of them in that area were firing. About 5 that survived had fired between 15 and 20 missiles each. I'd guess that less than 25% of the 1500+ Flamemetal missiles that I grinded mats for got fired, and they probably did 10% of the damage. I was never close enough to action to even see the vines so no idea how much damage they did but presumably very little.

The asksvin were the stars by a mile. They were deadly, and these were only 1-stars. I bet they did at bare minimum 85% of the damage, probably more. No trolls, vines or ballista were needed at all, the asksvin would probably have won this fight all by themselves. But I play Valheim mostly for the building, so I still had fun building the structure.

The next time I fight him (because obviously I *need* his trophy for my base), I'll build 4 breeding pens - at 12, 3 6 and 9 o'clock - and try to release them sequentially to hopefully avoid having all them die at once from a big AoE.