[tinkthank]

I hate losing the riders of my spiders much less once I hit Construction 6 (which I want anyhow for skulls of fire) for this reason:

A Sorceror with a random water and a water bracelet can cast summon bog beasts -- supplemented with a few unroutable vine ogres (sorc with a random nature or a thisle mace) -- which in my opinion are a GREAT bang for your buck, IF you have poison-immune units, and those are cheap vine ogres and....
riderless spiders! Save em all, and make a cheap poison squad! A leader or two with a snake ring can then cast decent poison spells as well with impunity -- spiders and bog beasts rock!