Location: around the Howler hole near the eastern portal in Mount of Hero North
Tactic: Typically tough Howler with nasty poisons and fast retreat moves (very likely actually the retreat bug). Warriors simply rely on their Warcry, Rouges need to be careful while dodging heavy at range, while Mages should try to take it slow and rely on massive selfheal for TCOS Gold.
Zack the Zealot 55/3 (quest not available)
Type: level 55/3 Glaspail
Location: around the Howler hole in Evhail's Haerth in Mount of Hero North, although often eaten by local wildlife
Tactic: Fair mix of melee and magic attacks with decent damage, slight AoE. Quite doable, but avoid disarms and fight in the opens - he is very prone to the retreat bug with all those trees around.
Ferrus
Type: level 55/3 Ancorr
Location: patrols the Shard edge of the western island in Desolate
Tactic: Has very few HP and can be nuked - just disarm it or precharge a combo.
Jhryux L'niar
Type: level 55/3 Vhuul
Location: patrols the Shard edge of the Eastern Peaks in Desolate - note that the local wildlife doesn't like it, either...
Tactic: Has quite some HP in is quick on its feet, but only weak melee attacks and no special moves - easily controlable.
Daahn Daaevid (quest not available)
Type: level 55/3 Ghost
Location: patrols between the Deslandes Estate and the northern ruins in Slywood
Tactic: Casts magic and has melee moves - hits not particularly hard. Just remember dodging and debuff physique if you want to stay in melee.
Waya (quest not available)
Type: level 60/3 Wolf
Location: patrols on a east-west line between the tavern and the Tree of Ascendance in Slywood
Tactic: Hit's viciously and is hard to dodge. Use Disarming Strike / Mind Blade / Vile Hunt & Ante Opener. Watch out for the wildlife around it, especially the roaming cats.
Hyonia Shurinai (quest not available)
Type: 55/3 Aronite
Location: partols the northern Knifewilds in Mount of Heros South around the little Aronite encampment
Tactic: Has strong ranged attacks, including one that applies a burn. Best ambush her afar from support and close quickly to melee, where she's rather weak. Sometimes is not attackable, then just follow her a bit until she debugs.