RECOMMENDATIONS
Recommendations are for new characters or those who are yet to do mission 3 of Blood Brothers Quest. If the character is thrown into the sewer DO NOT go to Julius, return to Armenius’ tavern and pass over the 2 sqms of the entrance, if not pulled into the basement, then go to Julius and continue your quest.
Unfortunately, there is still no clear way to obtain the achievement for those who have already completed the quest, but with the data from the conclusions you get a good idea of the process:
The Sqm does NOT activate from time to time (like Man in the Cave), it is always “active”, the problem is the requirement that the player must meet, now the question: what is this requirement? We came up with several theories, and after discussions, we believe that it involves stepping on some sqm near the counter immediately after a floor reset and returning to the exit (like something similar to what Lord Strikee did in this post), an explanation would be that in the case of floor reset is when Armenius would search for food, and find an unsuspecting player near his counter would activate his instinct to pull him to the moment he tries to leave the tavern (This explanation is based on ideas and has no proof).
The mechanic will possibly not be that different from how it occurred in these tests, probably game time, condition on the character (poison, burning, bleeding, etc.), room furniture or set items do not or will not affect the outcome.
Unlike what one would expect from theories that might suggest Armenius resembles Man in the Cave, the master vampire always spawns again every time a player is thrown into the basement and receives the achievement (this can be confirmed in each of the achievement screenshots in the gallery at the end).
If someone already killed/killed Armenius on the day you are testing don’t give up, it wouldn’t mean a problem since he can appear more than 1 time a day and that was proved in this test, check the picture below in which there were already 2 bodies of other characters that got the achievement minutes before: