Love Renfield and I run him in pretty much any investigator that can have him BUT I've also learned that you do need to be able to manage him safely to not screw your entire team. You got only 2 cards for that as well as the encounter deck and potential enemies on you. Me personally I love running Arcane Initiate in Marie together with Renfield and an addition to that Calling in Favors. Arcane Initiate comes out with a doom, like you want, and she helps you dig for spells you want/need like Moonlight Ritual to abuse more Renfield or get you that Shrivelling/Sixth Sense depending what your team needs. Her signature is also a spell which is a great target for the Initiate.
Love Renfield and I run him in pretty much any investigator that can have him BUT I've also learned that you do need to be able to manage him safely to not screw your entire team. You got only 2 cards for that as well as the encounter deck and potential enemies on you. Me personally I love running Arcane Initiate in Marie together with Renfield and an addition to that Calling in Favors. Arcane Initiate comes out with a doom, like you want, and she helps you dig for spells you want/need like Moonlight Ritual to abuse more Renfield or get you that Shrivelling/Sixth Sense depending what your team needs. Her signature is also a spell which is a great target for the Initiate.