This is a rules extension^Ex which provides rules for searching a 6-mile map hex for monster lairs.¹⁾

Each hex which is not patrolled by a settlement contains a number of lairs as indicated in the Lairs rules.

A 5-mile hex can be intentionally searched for lairs. Of course, not all hexes will have lairs, and it is impossible to know how many a hex contains at a given time without the use of magic. Because treasure types are used for outdoor lairs, it’s possible for a lair to be very profitable or to return nothing at all.

1. Party travels to the hex they'd like to search for lairs.
2. Every hour, two checks are made:
   1. Lair check: The DM checks with a d20 on the below table, based on party daily movement speed.
      1. If a ranger is in the party, the check is at +4. This bonus is reduced to +2 if the party is flying.
      2. If flying, a check is made every 30 minutes instead of hourly.
   2. Random encounter check: Random encounter checks are made every hour instead of at the normal times defined by DMG 47. These too can result in a lair via the monster’s % In Lair chance.

The party may split up, in which case the resultant smaller parties each get their own checks. These parties will not be close enough to assist in an encounter (without magic).

This system can be an attractive choice if an expedition completes with an hour or two to spare in a session and the party wants to do something other than start a new expedition. In that way, it's similar to the treasure maps system. Sometimes, a group might want to do this for an entire session, since it can be a fun interlude from other things, and is basically always an option.

DMs may desire to roll up lairs in advance for each of the hex terrain types (see Appendix B), and then use them when lairs come up on a hex. That being said, this can certainly be done on the fly. Though there is always the chance of rolling a Men lair, which typically involves a lot of rolling for the classed characters' magic items.

How many lairs are in a hex? Extrapolating from Dave Arneson's system:²⁾ roll a d10: 1-4 = that many lairs, 5-0 = no lairs. Players should of course not know how many lairs are in a hex.

If a hex is determined to have zero lairs, yet a random encounter in that hex hits the % in Lair roll, the lair can still be placed if you'd like. It must be a new lair that's just popped up!