Empty slot for primed smites, or you can go quickening/[Gladiator Might] if you prefer.
If this is umbra version, just drop the heat mod for sac pressure and go heat color on your frame.

Corpus go radiation with cold on the frame or pure toxin on both melee and frame

This is of course to be paired preferably with a viral+electric primer

Warframe Here: https://overframe.gg/build/146124/excalibur/general-exalted-excal/