When the 4 X-machines combine, they formed a larger mobile humanoid weapon called the XRX which is meant for WMD and taking down larger enemies like warships and large mobile weapons. With 2 fusion reactors from the X-2 and X-3, the XRX is 3 times powerful than the previous SRX and emits more energy output. In addition with better coolants, energy optimizer and refined T-link systems, the XRX is proved to be more efficient and packs with powerful blows.
Like the X-1, the XRX can also channels and harness TK energies to her fists and chops to deliver deadly blows to enemies her sizes. With the laser cannons from the X-2, she can mounts barrage of attacks on smaller enemy groups. Finally, with the refined G-sword divider from the X-4's module-the XRX's utlimate close-range weapon which can slice a warship into 2 halfs.
After the XRX's TK field and gravity field override, the XRX's armors change into shades of black due to increased electromagnetic field. In the Solid form, the XRX is twice more powerful and twice stronger at endurance but slower than the normal form. There's also a short time limit to maintain in that form as the pilots can only endure the gravity pressures for only 10 minutes.
Well, that's all the X-series combiner units for now and boy, that was fun back then. Hope you enjoy it