If you want to be able to rip through their armor and massacre them easily for nameless venom, use basilisks, their poison spit rips right through their armour and can kill them too depending on how high the basilisks damage is. Use these against them
When about three spawn, one will turn into a alpha, ( large and orange) which are the ones that drop the venom. WARNING: When they drop the venom, a bag will drop with the venom inside, it won’t go into your or your tames inventory!!! If ten spawn, a reaper will appear. Keep a light pet with you so they don’t overwhelm you. Light pets will burn them, doing major damage. That’s really all you need to know to fight them!