I see Sir Lindeal pops as a roaming mob even though he has a static spawn. Have yet to see a lesser nightmare in about 4 days of camping yet have killed Tisella 3 times, I have a full suit of Brognot armour and am opening a shop for lizardhide boots, and Sir Lindeal himself hates me so much he's gone to Qeynos and has hired someone to come after me. No lesser nightmare yet though... I hear reports of people killing him, but he seems super duper rare!
