I wouldn't be surprised if the venom was addictive too. I mean it isn't like it had any selective pressure for preventing or causing addiction. Although the lat

I wouldn't be surprised if the venom was addictive too. I mean it isn't like it had any selective pressure for preventing or causing addiction. Although the latter may come as a side effect. I can see a purpose for a multifaceted venom - both synergy of "speedballing" the lethal dose and making it harder biochemically for a creature to develop an immunity. Like always with evolved systems purpose is an emergent thing by what reproduces and survives the best. It is a tautology of "things that spread and stay you have more of".