Pls explain how early summoning spells are useful

[Blitz]

Behemoths are expensive, but very attainable in the early-game, and come just one level after raise skeletons at Enchantment 4. I like to mix behemoths in with my C'tis troops on my way up the enchantment tree. While early summons are rarely cost-effective when compared to their late-game counterparts, there are a few which stand out in the death tree. Outside of death, I rarely if ever use summons except the occasional seasonal while desperate and under siege.

[Aleph]

Certainly, look carefully at nationals. Mictlan, Agartha, LA Pangea, likely others live and die by their national summons, even early on. I'd even go so far as to say that the whole reason to play EA Agartha is their ridiculously efficient and easily summoned nationals (well, that and the mix of Blade Wind and Magma Bolts that their Earth Readers can toss around).