A gas turbine engine including a first turbine rotor assembly having a plurality of first turbine rotor blades extended within a gas flowpath, and a second turbine rotor assembly positioned aft along the gas flowpath of the first turbine rotor assembly. The second turbine rotor assembly is rotatably separate from the first turbine rotor assembly. A casing surrounds the first turbine rotor assembly. The casing has a unitary, integral outer casing wall extended forward of the first turbine rotor assembly and aft of the first turbine rotor assembly. The casing includes a plurality of vanes extended from the outer casing wall and through the gas flowpath aft of the first turbine rotor assembly and forward of the second turbine rotor assembly. The casing includes a plurality of walls forming thermal control rings extended outward along the radial direction from the outer casing wall. The outer casing wall and the thermal control rings is a unitary, integral structure.