I'm so glad this question was bumped up! I'd really appreciate a site with just hints about quests, not full spoilers. When I solved this quest myself, I just relied on general directions, logic and try and error.
The quest actually starts from Costello and a search of Brother Fugio. The Monk's Diary contains an introduction and instructions how to open the magic walls at Ghostlands.
The Seal of True Path and the Seal of the Demonrage can be easily solved by trial and error. Try the first square/lever: if you're correct: remember the step; if you're wrong: get punished and repeat known steps.
The Seal of Sacrifice: the name is the hint itself: the Queen of Banshees will mention it. Blood needs to be spilled...
The Plague Seal has a hint just north of the teleports: two pearls are embedded in the rock.
The Seal of Logic is based on spotting the pattern (similarly to IQ tests). The pattern there can be interpreted as a subsequent numbers written in a ternary numeral system. In each column 0 is represented by no flames, 1 by just the bottom flame, and 2 by both flames. Contrary to Arabic numerals, digits go from left to right. Turning on just the upper flame is not a valid digit. So, each spot represents a value of "left_column + 3 * middle_column + 9 * right_column".
At each step, the signs contain the same value as the flames, but written in roman numerals.
I kissed a banshee, I liked it...
~ Alip Aldo