@Old Man Loki - does it need updating? Have you tried it?

update please

A nice idea, but I think that this additional buff should go to the pirate cove building which is by far the most niche and underused, i.e. Corrupted Tavern. The other ones are in a good spot. Hideouts and Coves are very good for money and research. The Den is essential for hero cap and useful for lord recruitment cap. The Tavern doesn't have anything special, though. No money, no global buffs, just local vampiric corruption which most of the time will be a worse choice than the other options. So how about giving the bonus to this building only, but sth like +2 or +3 instead of +1?