Ghostlore

There are actually 36 levels to beat to get this achievement. If you die before finishing a floor you restart at the beginning of that floor.
1-1 to 1-5 + boss level
2-1 to 2-7 + boss level
3-1 to 3-9 + boss level
4-1 to 4-11 + boss level (achievement pop after all bosses die)

tips: ignore all mobs and walk around the floors till your find the boss. No point in farming these enemies. At my level (112) and with the perks of 12 legendary glyphs and 4 gems in each gear give me, mobs ignore me unless I bother them.
Bonus: avoid getting stuck in rocks, that's a really frustrating way to die. :(

Following the guide for lvl 10, you will need to beat Hell 4 in order to obtain this achievement.

Hell 4 has 11 levels + 1 boss zone at the end.
Once all 3 bosses are dead the achievement pop.