Sharingan eyes took notice of the spawning of a small forest, the creation of clones, and said clones being directed towards him. Having his eyes easily follow everything, all there was left to do was react. The Yondaime started by quickly dashing away from the original kage and said clones who were moving towards him. The Yondaime was typically a distance fighter, and would seek to create separation. Considering his virtually unlimited stamina and endurance, he would keep rapid movement up for a very long time.
Once adequate distance was created (About 20 meters from the clones, should they attempt to follow, else 20 from you) the Yondaime would come to a hard skid, his feet dragging into the ground. As he stopped his movement, the Yondaime would slam his hand to the ground, causing a moderate amount of smoke to propel into the air. The smoke would clear within seconds, revealing the Yondaime on top of a giant clam with an Otogakure symbol etched onto it's shell.
Without hesitation, the clam would begin expelling mist through it's siphons, albeit a purple one. This clam was a variant of the typical one, and could expel Otogakure's secret hiden Dokuton through it's vents. The mist would quickly cover the fighting location in a matter of seconds. The Dokuton when it comes into contact with any organic matter (except the clam and Yondaime) would seep into said being, and infect their chakra network, "eating" it till it ran dry. This meant Kage, his clones, and even his Mokuton forest were targets.
It didn't end there, the mist produced also had a genjutsu effect, able to manifest realistic mirages using the mist exuded by the clam. Making it difficult for observers to distinguish from the real thing through normal methods, this would serve to hide the location of the clam and Trev, who would quickly move from their original location once the mist was expelled.
In an attempt to confuse Kage, various images of the clam would appear in the distance, away from where the real clam was. An image of the Yondaime would also appear from the mist, charging a short distance away from Kage, an attempt to distract him as he would think a nearby threat emerged. Of course Kage, had the sharingan, but since the mist was constant, any attempt to break it would result in him being put back into the genjutsu until the mist was cleared.
Thus by the end of the Yondaime's actions, Kage faced several issues. One, could his sharingan sense the real Trev and Clam (Debatable), did he know enough about the jutsu to not try and continuously break the genjutsu and aim for the mist? Several mirages would attempt to bait and distract him. And finally, if swallowed by the mist, his chakra would slowly start to drain. For kage to survive, he would have to answer these issues, made much more difficult if he did not know the nature of Otogakure Dokuton, or the uniqure nature of this clam.
Summoning: Giant Clam
Demonic Illusion: Steaming Multistoried Building (Dokuton variant)