The phrase "I'll see you in Valhalla" refers to a concept from Norse mythology. Valhalla is the hall of slain warriors, a majestic hall presided over by the god Odin. It is depicted as a warrior's paradise where those who die bravely in battle are welcomed to live blissfully until Ragnarök (Doomsday), when they will fight alongside Odin.

In modern use, the phrase is sometimes used as a tribute to fallen comrades, especially in military contexts, to honor their sacrifice and courage. However, it originates from a very specific mythological context and does not align with all cultural or religious beliefs. For example, it was notably used by FBI Director Kash Patel in a tribute to Charlie Kirk, a Christian, which sparked discussion due to the cultural and religious differences involved.

In summary, "I'll see you in Valhalla" means that the speaker hopes to meet the person again in the afterlife, specifically in the warrior's paradise of Norse mythology, honoring them as courageous and worthy like a heroic fallen warrior.