Long time lurker, first post.
Snatched a first victory in EH against Yogi a few days ago. Just want to clear an incident.
During the play an investigator got an encounter from Tokyo which allowed to reduce one monsters health by 3. Would that allowed to reduce an Epic monsters health also to the point of defeating it (monster in case was the Dunwich horror which had already had damage done to it)?
I wasn't sure so I dropped another monster instead.
Defeating the DH solved the second mystery so I didn't want to cheat my way into victory.
Yes, you can reduce an epic monster's health like this. See the FAQ
Q. Can the Agency Quarantine Asset or the Shrivelling Spell cause an Epic Monster to lose Health?
A. Yes. Effcts that cause Monsters to lose Health, such as the Agency Quarantine Asset or the Shriveling Spell, can cause Epic Monsters to lose Health.