Goddess Lena had never punished her slave before and as she plotted what to do to him so as not to let him get spoiled, she felt that using dirty feet on him would be appropriate and would get the job done. So she got her feet dirty and then got him to lick them clean and just as she had hoped it would work, it did and he got the message.
Goddess Lena wanted to make sure that things went her way and that is why she had to teach this loser a lesson he had not been taught before. She did not want to spend a lot of time with him and that is why she went for a cruel punishment once and for all. So she turned her boot into a humiliation tool and she made him lick the dirty boots until he did what she wanted.