'step by step did arissa , guided by zalasta , lead the chaplain down and down until all semblance of decency had been washed from him , and then it was that the styric proposed the ultimate degeneracy - that the lustful princess , aided by her now equally foul paramour , should seduce thy father , her brother , and when he should be wholly in her thrall , should she broach the idea of incestuous marriage to him .