Actually I think we just all ended up in the same mission by chance, there aren't that many among the many characters that are such. of course while Maher is Templar trained and an inducted member of the order, he may not be the strictest adherent to dogma...

...Still a demon appearing before him is likely to trigger something.

On another note i still find it amusing that so many still think the Sea of Blood has any water in it at all. The name is not just a name, its actually a very accurate description.