while having both bloodmoon and primitive mobs installed, during the bloodmoon event, the flame spewers will spawn in the overworld, outside of lava, a lot even in high light levels, ive tried blacklisting the mob from bloodmoon but it still spawns, ill try posting this on the bloodmoon's mod thread too.

Did you ever get anything back on this? Although I'm fairly certain this is my fault, it is hard to track down without knowing how Bloodmoon would force these to spawn... I might be able to do some safety checks.

i wasn't able to fix it, bloodmoon had some weird things happen so what i did was: i whitelisted the vanilla mobs because i couldn't blacklist the spewer. another thing i found is that even disabling the spewer from this mod, the bloodmoon mod tried so hard to spawn them in that they would spawn for an instant and then disappear (because they were disabled in the first place). its weird.