That is what I did. I only attacked the Boss.
The spiderling stacks had a size of 300 at the end.

My tip: Take two armies of snakes with you (royal/swamp), which you place in the middle of the battlefield to take care of the spiderlings. They are poison-resistant.

Just curious how much damage these trolls should do on the big spider, when I was trying kill him with this tactic my trolls were doing something between 190 to 250 which is not much. So I gave up that and kill him with the axe, the trolls were just for mana regeneration.

With the help of this thread, I choose my troops. witeAnd I finished the war with this and luck under 10 rounds.
Make Hilda senior for leadership,Then I used the wanderer skill (flaming eyes)which gives +%20 leadership. Also have gloves which gives +10 poison resistance.

I use ancient bears, polar bears, vikings, berserkers and 4 jotun. There were good choices except jotuns. I used berserker and stone skin. It is an amazing spell. With my luck when I use berserker, the troops always attack the giant spider with 2000-2500 hit points. I can't beelieve this and The giant spider dead quickly. Bears ann the others kill the babies immediately.

Soothslayer, impossible, level 22
Didn't have glory. Around 5500-5600~ leadership
Went with Maidens, 3 types of snakes, 3 Trolls(out of 5).
Everything got slaughtered but a few snakes and the trolls. Ended up with stacks of 500...
But I still got it :)

Snakes aren't 100% poison resistance, but those units are still good since they can usually attack without being counterattacked.
But for that strategy to work, frenzy seems a must (I didn't have it). Trolls will be good regardless.

I can give this tip through
I got the high level by getting learning asap and using XP items and A.K scrolls.
I also sacrificed items to the rage valkyrie who at level 4 will give a quest to kill 10 orcs around the northern islands.
It will give high amounts of xp and +2 Intelligence from killing 10 orc groups (for soothslayer).
The strength of the orcs seem to scale at the level at which you pick up the quest from the valkyrie. The experience scale on their armies.

I went from not being able to beat the Spider to doing it no loss using the Trolls. I think it ended around Round 69 for me.

soothasyer level 19 -leadership 4800 - beat it with :
royal snakes 80
jarls 15
jotuns 3
polar pears 32
assains 33
distoration magic 2 order magic 2 with no defensive spells except avenging angle
using 2 wanderd spells : gift of stone and fortinue smile

I loss most of my unites exept 1 jotun 28 snakes 24 assains

Spider fight hot to get trolls always?
 

Hello
On this movie : http://www.youtube.com/watch?v=3KgxbBBrdRw
I explain no lose tactic for mage and how to get trolls ALWAYS when You got scroll call 5 level monster.
On my youtube channel You can find a lot movies with fights against hardest oponents in the game (Von varro, Magnikant,Dedred etc.)
All battles and all the game no loss 8-)
BTW Any1 of You know anything about WotN editor? There it is any chance to get?buy it?

Without Mana spring ?
 

The trolls solution is good if you have the mana spring spell. Without it, you can't use 3 trolls to do no loss.
3 of us succeeded with 3 different solutions, related here :
http://forum.1cpublishing.eu/showthread.php?t=36157

1. I used 4 trolls not 3
2.I havent used any mana ressurect spell just bought all offensive scrolls on the map from all vendors, it should be absolutly enough.

Finished all game as mage on impossible difficult with no loss then I really know a little about this game.

Visit please Jarcik bounty Youtube channel. There is a lot of HD movies about that including all hard fights.