[quote=@Crusader Lord]
[@Cu Chulainn] Speaking of which, what sort of "compatibility" are you looking for in a servant for your master?
[/quote]

The Fuyuki Grail system (which this Grail is most likely emulating, imo) chooses a Servant that matches the Master's personality the best, should the Master not have a proper catalyst for summoning. 

In this case, I was hoping for a servant that matches Hasabe's personality well enough. If there isn't really any servant like that (of which he could summon), I'll probably just throw in the catalyst somewhere in his bio and have him summon a random servant through that 😬