The flames around felt as hot as the real thing, smelled and sounded as the real thing to. Moving fast, Harry threw himself backwards, through the flames behind him and away from Remus. It might burn, but he reckoned through fire it was better than surrounded by it, even if it might burn. Rolling on the ground he used his position temporarily turn the ground under Remus into ice, impossible to keep your balance on and followed it up with a volley of stunning spells as he got to his feet and jumped out of the way from any possible new hexes.
He knew he needed something to balance off against Remus' sharper senses, but possibly also use those senses to work for him. Without the need to aim or hit Remus, he and cast a Muffliato. It would take care of sound, filling Remus' ears with an incessant buzzing that Harry could only imagine would be worse for Remus than others. It wasn't what it was designed for, but if he could use it, he would.