Board Thread:Theories/@comment-32041498-20170518152701/@comment-30632294-20170620171138

I came to the same conclusion. I actually think it's one of the strongest reasons you don't want to mix Shifter powers (i.e. The theory that Galliard ate Ymir when he already had a shifter power). Once you mix them, the only way to split them out again is to give up control of the titan. This is a massive incentive to do exactly what the survey core did to Bertholt. Defeat the Titan, render the shifter unable to shift, feed to pure titan.

It really makes me wonder how Marley gained control of 7 titans in the first place.