Titans- Can't survive long on a plane

Kiora looked up at the tendril-dangling membrane the titans had become—and she could see the cracks spreading across their forms. The glyph spell had formed a connection between the titans and Zendikar, and the leylines were slowly, gradually eroding them. They were beings of the Blind Eternities, and being dragged fully into this reality was tearing at their very existence. The titans, finally, were beginning to break.

But at the same time, the land of Zendikar was breaking as well, and far more rapidly. The air was a storm of broken gales. The sea was swirling into waterspouts. Kiora knew that the land under their feet would be the next to dissolve.

(Zendikar's Last Stand)