Board Thread:Wiki Discussions/@comment-25217769-20140723231559/@comment-4271790-20140801200355

So the TSBs requires the TT chakra (a huge mass of natural energy) or the chakra of the nine tailed beasts and senjutsu (another form of big natural energy). So basically, TSBs require huge masses of natural energy, or senjutsu to the highest point. This is what I meant by Indra and Asura being "special cases:" Sasuke and Madara needed the EMS to unlock the stabilized Susanoo, while Indra just needed the MS. Naruto, Madara and Obito needed the Ten-Tails chakra and/or all of the nine tailed beasts chakra and senjutsu to use the TSBs, a huge amount of natural energy either way. I'm thinking Asura, being a special case like his brother, was able to use that huge amount of natural energy to unlock the TSBs. Asura and Indra didn't need those extra powers. They were unique. Indra could use the full power Susanoo with just a MS, without the EMS, so I think Asura could use a huge amount of natural energy without the TB chakra, that's what I mean by "special cases."