Rusaku’s eyes would widen as he was overwhelmed by the sludge like substance; a wave of panic almost washing over his usually calm demeanor. Looking to the bodies his heart would skip as he noticed his surrogate parents Fugaku and Shima, his friends from the leaf, and various faces from his beloved clan floating about. Their festering bodies sending chills down his spine.
Then the illusion faded, and the two men would be standing in their original positions. Such as Bocchiere had surmised, Rusaku was able to retain his sanity in the face of overwhelming evil. Instead the opposite effect would take place.
Reaching up Rusaku uncliped the last button of his cloak, allowing it to float away in the wind. Slight hints of chakra could be noticed woven into it’s fabric. “So...that’s how it’s going to be?” he muttered to himself. “Then I guess I have no other choice but to end him, without hesitation.” The nightmarish illusion would have only strengthened the resolve of the Otsutsuki, for Bocc showed him a world that could become a reality if he were not stopped here and now.
With a determined mind, Rusaku quickly came up with a tactic based off the opponent's mannerisms thus far. Considering his entrance, one could hypothesize that his preferred element would be Katon. This was a detail Rusaku could work with.
With his right hand, Rusaku formed half of the tiger seal causing a sudden shift in the zones weather. Oxygen levels would begin to decrease exponentially, reverting to a third of the usual amount at sea level while the temperatures would drop just as quickly. If left unchecked, within seconds (Rusaku’s next round) the temperatures of the area would decline to an uncomfortable 0 degrees fahrenheit. It has yet to be determined if they would need to drop lower, but considering Bocc’s attire, one could assume Zero would do enough damage. Then when you count the previously stated winds, now becoming cooled by the dropping temperature, would soon create a windchill of -19 degrees. These conditions would make it so exposed skin would become frostbitten after 30 minutes. Despite the lengthy time one must wait for the skin to freeze, the temperatures would still make for hindered flexibility, numbed nerves, and a number of other side effects. Luckily Rusaku would be safe from these effects due to his specially crafted gear made just for conditions like this.
Now assuming all had gone according to plan, Oxygen would be in an incredibly short supply. Just because Bocc was essentially immortal, did not mean he was safe from all of the human body's weaknesses. Without proper time for his body to acclimate to the new conditions, he would be hard pressed to maintain the necessary oxygen intake to remain conscious for very long. Not only that, but he would soon become wracked with nausea and immense headaches if left unchecked.
Alas this shift in weather would only be Rusaku’s first action, thus he would continue. With his weather shift coming into effect, the Sannin would manipulate another facet of his Tenki sosa via a snap of the fingers on his free hand. Suddenly a vortex of baseball sized bubbles would move to engulf Bocc seemingly from thin air, each bubble exploding with enough concussive force to knock a full grown man onto his back while also drenching him in water. This drenching would serve several purposes. The first to either goad the man into using Katon to evaporate it, or should he take the attack to drench his body so that the cooled temperatures would affect him on an even greater scale. Hopefully the concussive nature of the attack would also limit his ability to form hand seals properly.
Finally, Rusaku would cause his hand to become engulfed the by his Tenseigan chakra cloak, condensing it into an orb that was about the size of a basketball. Rearing back, he would launch the orb in Bocc’s direction at 90MPH. It’s effects would be unknown to him at this time.