Allow the Oracle to tell you where certain unique monsters are currently located. Internally, this works by setting a variable that represents the floor the monster was last sighted on, which gets set when you leave a level with that monster on it and the monster does not follow you. When the Oracle is asked to find a monster, the code first scans through the migrating monsters list to see if the monster is heading to a specific floor, and if it appears on the list she just tells you that level. But if it’s not on the list, the code checks the last-seen variable for that monster, and if it has been set, she tells you that level. If it has not been set, you have never been on the same level with the monster and can’t have encountered it yet.