LEVEL: TIER
1-4: Student (apprentice, page, jack, novice)
5-8: Professional (journeyer, squire, adventurer, expert)
9-12: Master (knight, chief, senior, dame, sire)
13-16: Great (arch, archon, leader, grand, champion, noble, lady, lord)
17-20: Legend (marvel, superior, sovereign, world class)
21-24: Epic (luminary, sublime, exalted, immortal)
Suggest inworld titles and nicknames for any tier.
Each tier has four levels, matching proficiency and feat schedule.
I use the term immortal less often, because many non-epic creatures are also immortal.
Note, it is pretty close to BECMI, except it is BEMCI, since to me champion sounds like a winner among masters.