Is the dryad supposed to be in her lair only 10% of the time?
according to ACKs and some other sources, such as AD&D MM1, yes. Although i too wonder about the percentage chance, since dryads do not normally venture too far from their bonded trees…
I think in this case the “lair” is not her tree but a little grove with other dryads. The 10% make sure that the fluff text actually fits: “they are generally solitary, up to six dryads may be encountered in one place on rare occasions”
“rare occasions” in this case means less then 10%
Rodriguez nailed it.
One of the deadliest wandering encounters in the playtest campaign was with a lair of dryads... Heh.