Queen Agorath is an incomprehensible  goddess-behemoth that resides in the hadopelagic void beneath Creation. Nobody remembers how or when she became Queen of Albion, but inquirers into that particular subject have died in sufficiently discomfiting numbers that more or less everyone has stopped trying to figure it out. By all mortal measures, the Queen is quite insane, but despite a few fits of psychotic pique every few centuries, she does a rather passable job of keeping the country running, and her mortal Council can be counted on to attend to the details that might slip her royal mind.

Queen Agorath is the goddess of black magic and bodily transformation. Her Royal Clerics can only cast the reversed versions of reversible spells. They cannot Turn Undead, but can transform into creatures. 

When a Royal Cleric eats a beast’s heart and succeeds a saving throw, she gains the ability to transform into that creature once per day for 10×level minutes (a number of Turns equal to her level), gaining all its powers and abilities for that time. The cleric receives a +1 bonus to her saving throw for every ritually significant step she takes while eating the heart; the Queen’s ritual sensibilities tend towards the perversely elegant and darkly sumptuous.

from tale of tales

Examples:

  • Eating the heart off of a plate of precious metal
  • Eating the heart while dressed in an luxurious gown
  • Incorporating the heart into exquisite confectionary
  • Being fed the heart by silent and finely-dressed servants

Eating the heart of a creature with more hit dice than the cleric has levels does nothing. Furthermore, a cleric’s flesh can only remember so many shapes; a Royal Cleric can only learn a number of forms equal to half her level rounded up. Successfully consuming a heart while at this limit requires that she forget one of her existing forms.

from bloodborne