Two of Rhea's cult titles were Great Mother and Mother of the Gods. She was early closely identified with the Phrygian mother-goddess Kybele, whose orgiastic cult was introduced into Greece and which seemed to have included nocturnal mountain rites with much drinking and frantic dancing (yes, her cult was related to that of Dionysos. According to some, Dionysos was actually mentored by Rhea/Kybele).
The Homeric hymn to the Mother of the Gods says that: "She is well-pleased with the sound of rattles and of timbrels, with the voice of flutes and the outcry of wolves and bright-eyed lions, with echoing hills and wooded coombes". That is why I have drawn a lion and a wolf beside her.