[quote=@MeteorD]
Also could someone clarify which the current Masters / Servants in the HGW are? I'm not sure which of those in the Character tab is considered inactive / expelled.
[/quote]

The list is currently updated. The situation of Hisoka is currently a bit nebulous, since he's partnered with Cao Cao technically but as Cao Cao's roleplayer has dropped out, has temporary control for a bit.

With that said, the roleplay is currently engaged in a boss fight if you weren't aware, so summoning is currently ill-advised.