Stryder said
I'm making a Spartan :3 I think we are supposed to make them seem to have existed already in the ME universe so maybe, the Sangheli conquered the Taurians?
Just a quick note on that front? In the Halo universe, Spartans were designed to be genetically and technologically superior to regular soldiers, meant to stand up to -or surpass- the Sangheli Elites. However, everything that made them so powerful in Halo (Shielded armor, genetic/cybernetic enhancements, etc.) are commonplace within the Mass Effect Universe. Shepard was an extreme example, but most military forces have some sort of cybernetic enhancements (and all biotics do, in order for them to fully realize their abilities) and the majority of ME armor is at least equal to what the Spartans wear. Master Chief could flip vehicles and punch out Brutes, a typical engineer can throw plasma, and biotics can create miniature black holes with little effort.
It certainly makes sense that, after 300 years, there are at least some armor models similar to Spartan armor in the ME universe, but I'm not sure an actual 'Spartan' would stand out all that much amongst your typical council-race soldier.