There's a lot going in the Gallery. You'll see monsters in statue form, unable to move but able to easily hit you. After a certain number of turns (the count starting from when you first enter the Gallery), these petrified monsters will become free. Otherwise, the only enemies are Gorgons and their queen.
You can also find crystal display cases encasing items. These crystal blocks can only be destroyed with level 3+ BLAST.
The Gorgon Queen casts the same sequence of spells as regular Gorgons: GAZE to turn you into a statue and BLAST to crush you with insanely high damage. You could very easily die in one or two hits of her level 3 BLAST. When you hit the Gorgon Queen, Field Vipers fall out of her hair. These Vipers are actually the least of your concern and can't even damage you when you're in statue form.
Find a strategy that prevents you from seeing GAZE or from taking too many BLAST hits. A Blinding Potion will do the trick as well as a Silence Potion. Stunning or confusing the Gorgon Queen will work too. Another option is a guaranteed way to heal or remove statue form.