Lucifer's intentions

The reason why Lucifer wants to eliminate Cervantez before he can get any stronger is because of the heritage of his bloodline. The Hazelgroove royal family, although diluted over centuries has the blood of archangel Michael flowing through their veins. 

The first great war which Lucifer waged , was also because the moment the first Emperor reached tier 5 he was close to awakening the divine blood inside him . Very close to achieving true divinity . 

If Micheal gains a tier 6 bloodline descendant added to his ranks , then his half brother and the strongest angel would have another powerfull ally added to his ranks , something that Lucifer absolutely could not let happen. 

However , what could he do? , Being banished from the realm of humans by the four archangels and the goddess of life , he was confined to the depths of hell.