Hi, welcome to S.T.A.L.K.E.R. Wiki! Thanks for your edit to the File:All of them.jpg page.
Google Cthulu refs for Bloodsucker
And there was me thinking that all three were proxies for a certain previous SoS / Presidential candidate (failed - with oakleaf clusterfuck - twice)...
You are quite correct though: H P Lovecraft FTW.
No problem envisaged. Take your time. It's always nice to have context. (And I was injecting a little sarcasm - oh, what's that buzzing outside my window?..)