Macha is the cat character that appears in .hack//SIGN and other .hack series. Although she appears to be a typical hacker or Vagrant AI, she is actually an alternate form of the Sixth Phase Macha the Temptress. She lures Tsukasa to a secret area, where Morganna can then manipulate him. After the events of SIGN she takes on the form Mia who resembles an older version of herself dressed as a warrior, and goes on adventures with Elk to find aromatic grass because Elk resembles the boy in her dreams(Tsukasa) who gave her aromatic grass in the first place.
In .Hack//GU Endrance(an adult Elk) has the power to summon her true form into battle.