OK, so the kid did pretty well. He did have the weaker version of Horn of Valhalla, so he got 5 or 6 Berserks spawn to help him. He also used our custom Sticks to Snakes spell, which calls two venomous snake swarms that don't require concentration. So he had all that ready, and then got a surprise attack in with AOE spells. The 20 or so giants in Room 18&19 I think it was, were pissed and wanted at him. But he mostly blocked things off so they couldn't swarm him.
Deadlands maybe. Brom's art.
But I did warn him the Jarl, who he had spied, would hear it and come soon enough. Eventually 2 winter wolves popped in, with the Jarl and wife one round behind. They were held at bay by, one snake swarm, two(?) berserks, and the fighter. Chokepoint.
At the other larger chokepoint north of the party, looking into room 18 and 19, the kid first had used Spike Growth. I did some random rolls and more than half the guys near it did not notice it. And a lot of them even when they got hurt by it, just plowed through, thinking they were mighty giants.
DAMGE: Fire storm does some good dmg by the way. So does Crown of Stars, gotta roll to hit, but it hits a lot. The anti-giant sword + Barbarian frenzy raging + Amulet of Hacking (2 rounds gets +3 to all I think we said) = maybe 75 dmg a round if all hits and rolls go well.
DEFENSE: The dern Fighter got hit every single time I think, his 23AC did like nothing that whole fight, just unlucky. I almost got a first hit Crit on him by the Jarl, then we realized he shouldn't have been able to reach that easy b/c was so tight there with the wolves and doorway. But the wife did get a couple of crits I am pretty sure.
BTW, I used Firegiant attack stats for the Jarl + Cloud giant other stats (200 HP mostly). Used fire giant stats for the Jarl's wife.
Soon the kid did a wall of thorns, and it came into play a lot. I rolled impatience on the giants b/c they were mostly stuck, and a couple of them thought they could get through or over the thorn wall. Little did they know how magically painful it would be, and got nuked pretty hard. One time the warlock blasted one giant (lady) back into the wall from far, she went down from max HP to nearly dead (Hill giant stats, so like 105HP max) and fled the scene (she's going to show up later with the rezzed cloud giant probably).
I mostly had fun with making the giants kinda impatient and stupid. One was stuck behind the Cord looking giant, and he kept attacking the snakes in Cord's space which hurt Cord. Finally he jerked "Cord" away from the snakes but accidentally into the wall of Thorn, oops. Lol. Was fun for me.
It still was a darn hard fight. The Jarl + W.Wolves + Wife looked dangerous coming from behind, but soon the Jarl got his butt stomped by the Crown of Madness(?) spell which makes him see a super illusion and take a ton of psychic damage. The wife really hated snakes, so she wasted a round trying to attack them, before really wailing on the fighter and company.
The Fighter was knocked out right at the end. Rest of the crew were barely harmed if at all though. All the berserkers and snakes died, but did a good job up through the end.
So end result, it was a well balanced to be difficult but winnable fight with all the extras and all the lenient up front damage + 5 or 6 bersers and the 2 snake swarms, and the Jarl coming to the fight late, giants being a little too wreckless and stupid, etc., etc. As a DM I had fun, even though the giants didn't get to do anything interesting from a magic or attack standpoint, it was fun just having them be goofy bastards that kept making mistakes. Lol.