Done by the awesome  Spelunker_Sal

So in the latest story of Mac, where his brothers will make an appearance, He is under the triple threat's control (they are Piedmon, Myotismon, and Blackwargreymon) They control him with the 6 black rings that are on his arms. These rings forced him to grow another tail which gives him another transformation plus piedmon gave him the Zero sword, but is actually from ronin warriors more specifically sage's sword. The sword along with the rings has scrambled his mind, so all he knows is to listen to his masters and continue fighting until they say otherwise