I have only first level of rune magic, so my Ice spikes magic gives only three spikes and it's impossible to fill the whole battlefield. And I can't think of anything else
Is there no other way to kill the spider without losses? Doesn't nobody managed to kill it without losses with different tactic that filling the battlefield with spikes? I've beaten all the previous games without losses on impossible, and now I can't even kill the first boss on Normal. WTF?
edit : just killed it. Used only trolls split into three groups of one. Easy but long battle - around 50 rounds. Didn't like it, seems the tactic with the trolls is the only designed way to defeat the boss without losses.