Definitely agreed on the riddle difficulty
Is it the Grow Lance?
Triple twin chased - 6 linked materia slots.
Three and three score holds it - Something about it being on floor 63 of the Shinra HQ? Not sure how it actually ties together, though.
Transfixion it's case - It's a lance, ie. a piercing weapon.
Accretion defines it - The name indicates growth!
