It's a fight for survival, both for their brother and for themselves as the Crowe's continue into the pines. 

If you're curious about "The monsters that kill with their eyes", here's some references. I did modify them from traditional folklore to interact with Thaddeus's phobia. Plus, it seemed out of place for things to shoot lightning out of their eyes in Sounds Like Crowes.

This is a Hogan

The most fascinating thing I found while researching the Navajo is their creation legends. This link also contains images of their sand paintings they use for healing songs. 

The Coming of Monsters:
"In the Third World, there was a time when men and women had lived apart for a long time. During that time, some women had used animal horns or long stones or bird feathers for sex. Now, in the Fourth World, some of those women were pregnant. One woman who had used an antelope horn gave birth to a child with no head. The people held a council and decided that this baby would be abandoned. It was left to die in a gully. But it lived and grew to become Déélgééd, the Horned Monster.

A woman who had used an eagle's feather for sex gave birth to a round, headless child with feathered shoulders. A council was held, and it was decided that this baby too should be abandoned. It was left in an alkali pit. But it lived, and grew to become Tsé Nináhálééh, Monster Eagle. It made its home on Tséteʼiská, a peak beyond La Plata Mountains.

A woman who had used an elongated stone for sex gave birth to a headless child with hard skin and a pointed neck. The people met in council and decided that this baby should be abandoned in a fissure in a cliff. They placed the child and closed the fissure with rocks. But the child lived and grew to become Tsé dah Hódziiłtáłii, The Monster Who Kicks People Down the Cliff. It made its home at a place called Knol ghi nee, beyond the Carrizos Mountains.

A woman who had skinned a sour cactus and used it for sex gave birth to twins, headless creatures with no limbs. They had two depressions at the top that looked like eyes. The people gathered and decided that these infants had to be abandoned. They threw them as far as they could. But the twins found shelter in brush and survived. They grew to become Binááʼ yee Aghání, the Monsters That Kill with Their Eyes.

One monster came about in a different way. A woman named Loose Running Woman went off alone in the direction of the sunrise. After defecating, she used a smooth pebble from the river to clean herself. She placed the warm stone in her genitals just as Jóhonaaʼéí, the Sun, rose above the horizon. Seeing this, the Sun sent a ray into her. In only nine days she gave birth to a large child. Having no husband, and not knowing who the father of the child was, she abandoned the child in a rocky place. But Jóhonaaʼéí knew that the baby was his, and he protected it from afar but never visited it. The child grew to be large and powerful and very angry. It was called Yéʼiitsoh, Big Giant, by the people.

The monsters hid along paths, and killed and devoured travelers. They killed many people, and the people began to live in fear."

​The Crowe boys enter an unnatural forest, in the unlikely hope that their brother's salvation may lie within.

The Crowe boys must deal with a rising threat, as their journey through the Arizona night takes them ever closer to Tombstone.