User blog comment:Miskos3/Episode 272: Fairy Tail Zerø: The One Who Teaches Magic, Review/@comment-7418318-20160220145442/@comment-5303512-20160220151017

Well sounds like from what Zeref said about "strength of feelings" along with getting Ethernanos from around you, basically confirms that Nakama power is not a plot device but it is a factor in using magic power. Just like in Asura's Wrath where Mantra is based on prayers and power of emotions.