Eren used Life Drain on the swordsman to recover some of his stamina and mana back. His injuries would heal as well after using the ability. But he felt like he wasn't utilizing the Life Drain to his fullest potential. Plus, the two rangers were making it difficult to exercise his power in peace.
Claho was terrified after seeing Eren's battle presence and the way he had handled the whole thing. Technically, Claho held all the advantages. And yet, Eren was beginning to fight back in such a way that he ignored most of those odds that were against him.
"Attack... Fucking attack him, damn it. Kill him using whatever gears you have been given. Bring me the guy's head. That's an order."