Function and Meaning of the Karnak Hypostyle Hall

Seti I kneels to receive symbols of life, dominion and "millions of jubilees" from the falcon-headed sun god Re-Horakhty and the lion-headed goddess Weret-hekau. In return for his devotion, the gods promised the pharaoh an eternal kingship
"The God's Living Room"

The Karnak Hypostyle Hall can best be seen as a glorified vestibule, and even an introduction to the inner parts of Karnak temple beyond. Every wall and column inside is covered with inscriptions, displaying virtually a cross-section of what took place here. On some walls we see a sampling of the rituals that took place at Karnak. On others there are episodes of the festivals that were celebrated here, or at nearby temples. 
       Seti I defeating Libyan Tribesmen. War scene on the north wall of the Karnak Hypostyle Hall

War scenes on the exterior walls not only glorified the king as a warrior, they magically protected the temple by showing the forces of chaos- the enemy- defeated by the forces of cosmic order, called Maat led by the king himself.
Ramesses II offers four calves to the god Amun-Re. 

Endless scenes like this one of the king making offerings to the gods cover the walls and columns inside the Hypostyle Hall. In return for worship and offerings, the gods gave "life, prosperity, and health" to the king and to Egypt. Pharaoh plaid a unique role as the sole mediator between humanity and the divine world.
On a theological level, this forest of columns reproduced the primeval marsh that grew up on the first mound of land at the dawn of creation. It is a model of the Egyptian cosmos

Temples were designed to reflect these connections between the human and cosmic spheres. The Great Hypostyle Hall itself is not only an enormous replica of the sort of columned hall that, in private houses, was the master's receiving room: its 134 columns, modeled on open and closed stalks of papyrus, represent the marsh that stood at the edge of the island where creation first took place, making the temple as a whole a microcosm of the world as it was and, in essence, ever would be