Majere
Neophyte II
Tier Quests were introduced in the Stygian Abyss expansion. There are three NPC's that use this system:
On Heritage we have those like quest chains. You need to complete them in strict order here.
NPCs are located in Ter:

But acording to UO site and UOGuide :
So I created an account on OSI Europe and all three Tier 1 quest from Percolem were available (like Hertwood Quests: random on click).All of these quests are repeatable but you must wait a certain amount of time after completing a quest before you can get it again.
Acording to those guides when you open a new tier you just have more quest always available (with the cooldown time if you completed any).
BTW Percolem is Gargoyle on OSI while on Heritage he is Human..