Rororo

Rororo is a four-headed hydra and the pet of Zaryusu Shasha. He is very loyal to Zaryusu and the lizardmen as he sees them as his family, willing to lay down his life for them. Rororo was abandoned by his family since he was only born with four heads rather than eight and was therefore seen as weak. He was picked up and cared for by Zaryusu. After this, he has seen the lizardmen and in particular Zaryusu as his family ever since. (Source: Overlord Wikia)