I'll go with Shadow Flare Enemy Skill.

The last few lines of Riddle 1 seem to describe Ultimate Weapon emerging from the Northern Crater (near where Jenova crashed) and running amok. He starts at the crater near Junon, which you can't walk over, but you can fly over, but you can only fly as high as Ultimate Weapon. Riddle 2 clearly refers to the Enemy Skill materia.

I couldn't stop thinking of marijuana, by the way.