Before going into these steps, here are some basic things to do while fighting.

Do not heal while it is aggro, they will hit you before you heal. (Unless maybe you have quick focus or shape of Unn)

Spells are very good against them so keep up a lot of soul. If you have the soul, you probably won't even need this guide at all.

Do not try to brute force unless you have the health, you will take a lot of damage and might die. Or at least the other 10 primal aspids will kill you.

Kill the big grey bees, they give a lot of soul.

Upgrade your nail; I think a max nail can one shot it with a nail art.

If you do not have nail arts, replace the nail arts with just a regular nail. It will take longer, but it still will work.

Don't use cyclone slash for the nail art part.

Use shade cloak if you have it, but if you have shade cloak already, you probably don't need this guide.

If you don't have the soul, skip this step. Fire some sort of spell at the primal aspid before or after they detect you. If you are lucky it will die in 1 hit.

Try to stay away and wait for it to fire its first shot. While it is charging and firing, charge a nail art.

After it fires its first shot, quickly go up and hit it with the nail art. Dash slash or the big slash should work fine.

Repeat step 2 and 3 until the primal aspid dies.

If they are clumped together, you can attempt these steps with a bit more precaution. If not, flee, brute force, spam spells, or pray to the radiance.