Luach was born to Macbeth and Gruoch, some time after Duncan had succeeded to the throne during the unexplorered timeframe between 1032 and 1040; and, the first chronological appearance with him is in 1040 while he's exploring the hillside of his family's home with his father Macbeth & his cousins Prince Canmore and King Duncan.
Duncan, although unsettled by the thought, took Canmore with him when he went out hiking with Macbeth and Luach. Macbeth caught Duncan just as he began to fall off of the cliff putting all his fears of Macbeth killing him ease. Then they encountered the sleeping stone forms of Demona and several other gargoyles during the day. Duncan wanted to take advantage of the opportunity and destroy them but Macbeth begged that he spare them and his cousin reluctantly agreed. Duncan then called for Canmore and after saying that he was ready to leave as a thick fog fell upon them and the four then encountered The Weird Sisters who hailed both Duncan and Macbeth as "King of Scotland, and father of the King hereafter." Macbeth assured Duncan that he neither knew the old women, nor what they meant. And, after Duncan threatened the women with commiting an act of treason they told him that "... each of you shall in turn be king." Duncans' suspicions quickly flared up again as he thought that Macbeth might've wanted the gargoyles spared because they might be part of his plot to overthrow him. Afew hours later, Duncan revealed that he was the second Hunter as and a few of his royal guards soon returned to the gargoyle's lair just before nightfall. All but Demona and three others were destroyed before night came and they returned to life. Meanwhile Bohde warned Macbeth of what was happening and he feared for his safety and that of his family. Macbeth then willing to give his life to save them told Gruoch that he'd always love her and told Luach to, "Mind your mother." Fearing that something must be wrong Gruoch begged him to tell what was going on; but, he said that it was nothing and left Castle Moray.
Not knowing what to do next Macbeth found himself at the gargoyles cave and met the grieving Demona on a bog and pleaded her for her help. But his former ally who was now very old and infirm told him that she wouldn't help him because she had her own problems to deal with and that he would probably double-cross her anyway. The Weird Sisters suddenly appeared to Macbeth and Demona as two totally different beings and said, "This bargain calls for an act of good faith." They went on to ask Demona what she wanted above all else. Then they asked, Macbeth what he would be willing to give up for her aide. After creating the pact that bound them to each other, Macbeth easily defeated Ducan's forces with his human-gargoyle alliance. His first act as king was banishing Canmore; and, thus the first part of the triplets prophecy came true since who Duncan was once king is dead and Macbeth now was king.
After elevating himself to the throne with Gruoch as his Queen consort and Demona as his "Primary Chief Advisor", he decided that she needed a name and a fitting one for his new ally would be "Demona" because of how her fighting made him think of a demon. With Macbeth as king peace reigned in the Kingdom of Scotland for seventeen years with his Queen Gruoch, his son Luach and his soulmate Demona all by his side. But The Hunter returned for the third time into their lives in 1057 with Canmore now taking up the mantle. Canmore invaded Scotland with the aid of English forces. His initial attacks were held off by Macbeth's allied human-gargoyle armies lead by Luach and Demona.
However, Macbeth's father-in-law Bodhe was convinced that the English cared little for who held the throne of Scotland and were more interested in "purifying" all of Great Britain from the last gargoyles known to survive in it. Bodhe suggested that if Macbeth removed the gargoyles himself, the English would abandon Canmore to his fate and return to England. Macbeth doubted it, and Luach was completely outraged that his grandfather would ever mention such a thing as betraying the gargoyles; and, he was even more upset that his father would ever even consider the idea. Then MacBeth told him that a good king must consider all his options before making his decision. Still upset with them pondering that option, Luach left the castle to get reinforcements for the coming battle. This entire conversation was unfortunately overheard by Demona who concluded that Macbeth had already decided to betray her. So, Demona and her clan abandoned Macbeth and she allied herself to Canmore.
As all of Castle Moray's plans for defense were centered around the aid of the gargoyles, Macbeth's forces proved unable to beat Canmore's armies back. Macbeth and Gruoch managed to escape the burning castle; but, found themselves confronted by Canmore, one of his guards and Demona. While Demona accused Macbeth of betraying her and her clan, Canmore took the opportunity to stab Macbeth from behind. Immediately both Macbeth and Demona fell to the ground, apparently dead. Canmore concluded that the rumors of Macbeth's magical link to the gargoyle were true and that when one of them died, both died. He then admitted to his companion in front of Lady Grouch that he had already secretly killed the remaining gargoyles serving under Demona, and now with her and Macbeth dead and Luach's forces approaching they should depart for the battlefield.
The body of Macbeth was approached by Luach and Bodhe who took up the crown stating that "The king is dead... long live the king." and placed it onto Luach's head, fulfilling the second part of the triplets prophecy with Macbeth now dead and Luach as king.
The final part of the triplets prophecy is revealed at the end of "City of Stone" when The Weird sisters question Macbeth about what exactly does death or killing someone solve when they said, "...did your own death, save your son Luach from Canmore?" implying that both he and Duncan indeed became king and father of a king.