And also – to defeat them in one hit, you need to put everything in one slot, meaning your army needs to be twice as powerful. Otherwise, if it’s the other way around, the skeletons will scatter like fleas across 7 slots – then you definitely won’t have enough mana.
Справочник по НоММ-4 http://handbookhmm.ru/pamyatka-dlya-heroes-iv.html
Памятка по НоММ-3 http://handbookhmm.ru/pamyatka-dlya-homm-iii.html
и HotA http://handbookhmm.ru/vyishla-obnovlennaya-pamyatka-dlya-homm-iii-hota.html