Most cost-efficient conjurable units?

[Corinthian]

For troop summons in CBm its hard to beat the Hidden in Sand/Snow spells. You get some 25-50 elite undead troopers with heat/cold auras + a powerful mage on average. I once saw a single castings worth of hidden in snow troops (about 30), kill two kitted Zmeys in a battle taking only a handful of casualties. The cold auras froze them unconscious in 2-3 turns and even after loosing heads they could not flee. A casting of these spells cost 35/40 in CBM and the battle did not include the mage. Two kitted Zmeys cost around 90 gems by comparison.

[Torgon]

Originally Posted by Corinthian

For troop summons in CBm its hard to beat the Hidden in Sand/Snow spells. You get some 25-50 elite undead troopers with heat/cold auras + a powerful mage on average. I once saw a single castings worth of hidden in snow troops (about 30), kill two kitted Zmeys in a battle taking only a handful of casualties. The cold auras froze them unconscious in 2-3 turns and even after loosing heads they could not flee. A casting of these spells cost 35/40 in CBM and the battle did not include the mage. Two kitted Zmeys cost around 90 gems by comparison.

Problem is that you have to catch the Zmey with your hidden in sand forces. Not an easy task, and there are a whole lot more easy counters to undead than there are to a kitted out Zmey.