Hobgoblin

The change happened noticeably, beginning with white mana leaving Arthur's body and penetrating Mero's chest. As if he was shot with a bullet, Mero fell to the ground while clutching his chest. 

"Aagh!" He gave a pained scream as a dark green substance oozed out of his skin. He then started vomiting the same material as Arthur watched. 

'I should help him.' Arthur hurried to use the amplification rune to boost his stamina and then used the Heal-III rune to heal whatever damage that would happen during the evolution. 

His mana was eaten up as the screams died down to turn into labored breathing. A vapor then started leaving Mero's body and it started to shrink down. 

Mero was almost half of Arthur's height taller. Yet now, there was barely a foot between them. As the vapor cleared away to reveal Mero, Arthur was stunned by the changes.