FPS boss fights always look pretty dumb. He's 60 feet tall, why is he putting down a spark that is the key to killing him, why is he opening his chest etc etc etc.
There are legit lore theories on why he's doing all of those things (some are more than just theories). I don't want to get into too much detail, but he essentially wants you to kill him in a specific way to set specific events in motion. So yeah, pretty much everything about that end fight actually makes sense from a lore perspective. The Taken King lore is pretty incredible. If only Bungie let you read the lore in the game...
Whenever someone kills me in an FPS game, I always die on purpose to set specific events in motion too.
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