User blog comment:ZokeiR/Possible Grand Servants/@comment-28209103-20170422172711/@comment-4802891-20170422182727

Requirements/special skills... good point, we should go by that first. It's actually interesting to keep in mind these 7 super Servants might work as a team, and what you bring here is a good way to make this work.

If Saber has Anti-Beast weapons and Archer Anti-Star weapons, I think Lancer should have Anti-God weapons, designed to strike down enemies who are strong but not planet-sized. Or maybe something to deal with giant armies of Servant-tier creatures.

If Rider has Anti-Threat shelters, Caster ultimate foresight and control over magic and Assassin dominion over the cocnept of death, I think Berserker could be the trumpcard you keep sealed until all hopes are lost, a creature that fight 1v1 with a Beast, having no qualms in damaging the World in order to stop the threat immediatly. Wouldn't that be fitting for a mad warrior?