Mars gives Harry no time to adjust, makes no attempts to ease him into the use of his body. The spells, potions, make him far more open than that small plug alone could have done and slick still drips out of him, easing the way. Warm hands settle in tight holds on his hips, using that and ritual-created strength to effortlessly hold him in place. He tries, he does, if only to see if he can rock back into the thrusts, but he can’t move at all.