For this LoRA, there are 3 main concepts:

The Mistress offers the cage.

1girl, smile, eyes, panty, holding pink chastity cage in hand, sensual provocative atmosphere, teasing intimate expression,

The Mistress teases with the keys.

1girl, smile, eyes, (detailed small metal key, holding small key extended forward:1.1), sensual confident atmosphere,

The Mistress teases her slave.

femdom, smile, eyes, confident and teasing expression, hand on femboy's torso, looking up at bound man, small key pendant on chest, chastity cage on femboy,

Don’t forget to describe the face and poses in detail.