The Tower of Frozen Shadow presents a unique, but familiar approach to dungeon progression. Although the seven (or is it eight?!?) floors of the Tower of Frozen Shadow are split up into 3 group instanced dungeons (Shadowed Corridors, Umbral Halls, and Haunt of Syl'Tor), there are quests that span all three. Completion of those quests is necessary to unlock different floors in the Tower.
UPDATE: Added quotes from Gninja.
When you first zone into The Shadowed Corridors, you are faced with a mirror that allows you to travel to parts of the zone that you've unlocked access to. This means that your first time through Tower of Frozen Shadow group zones will be quite the adventure, and take a substantial amount of time. Later visits will require less time and you can skip any mobs which are tied to the access quests.
As with the Vigilant in Sentinel's Fate, completion of all of the Tower of Frozen Shadow group dungeons is necessary to gain access to the Tower of Frozen Shadow x2 Raid Zone.
From EQ2 Designer Gninja:
Each floor 2nd through 7th has a hidden/quested Named that is much more difficult than anything else on the floor. These are quest fights that unlock the 8th floor they are intended to be harder. They only drop appearance loot and are meant to be able to be skipped if you are just running the zone for loot/shards etc.
Only one person needs access to get into any of those zones. Including the X2. You gain access to the other TOFS zones by killing the last boss of the previous zone. i.e. Spectral Librarian Emiida gives access to Umbral Halls and High Priest Mohnt/Dizzina the Lulled give access to Haunt of Syl'Tor.
For Velks speak to Viglundr Doomforge in the Storm Gorge Staging camp to get the access quests.
Some players have lashed out in anger at the idea that some of the named mobs in Tower of Frozen Shadow only drop appearance gear when killed. However these are mobs which are normally only used for the access quests to unlock the Tower. Rather than leaving these as ignored mobs after doing each quest once, some appearance gear was added for those players who are looking for some extra replayability.
Beside the quest mobs, each dungeon has a healthy population of official "Named" creatures. These access quest mobs are of a similar difficulty to trash mobs and just provide something extra to do while exploring these massive zones.
Considering most NPCs that are triggered by quests usually drop nothing I thought adding Appearance items to them as drops would be welcomed. This is not the first time quests have been required for progression. I can take a look at making them able to be transmuted if you like. Otherwise you can kill them once to get the credit for completing the quest to unlocked the best gear in the zone and get AA then you don't have to fight them again unless someone needs the update.
Every zone has 5ish named that do drop loot.
All the quest/triggered named only drop appearance gear. They are access quest named not the typical clear the zone for loot named. They are optional.
Thanks to Brammator and Atan for help on this article.