The worship of numerous and nameless nature spirits was brought to the First Men by the Children of the Forest. After the introduction of the Andals' Seven to Westeros, the spirits were dubbed the Old Gods and the practice of their worship became limited to the North. The religion of the Old Gods has no organization, clergy, evangelical movements, or holy texts, but some traditions are passed down by their followers. Various actions, such as incest and kinslaying, are considered offensive to the gods. Weirwood trees with faces carved into them, called heart trees, are considered sacred. Prayer, oaths, and marriages are often performed in the presence of a heart tree. The faces were carved into the weirwoods by the Children of the Forest, but their meaning or purpose is not completely understood to humans. Once all noble houses had a godswood with a heart tree in its center, but many families that no longer follow the Old Gods converted their godswoods into secular gardens.