Honestly, straight up...
I think he was thinking "I want to approach my long-term crush dearest friend and see if he's alive without being possessed myself by a vengeful shade".
He knows he carries Ratatoskr's blood and is therefore more susceptible to transformation than Alphinaud (who is Sharlayan) or the Warrior of Light (whose only canonical backstory is "not from Eorzea", aka not Ishgardian). I think he was literally, foolishly, just thinking in terms of how to get through the next 5 seconds.
I think he was thinking "I want to approach my long-term crush dearest friend and see if he's alive without being possessed myself by a vengeful shade".
He knows he carries Ratatoskr's blood and is therefore more susceptible to transformation than Alphinaud (who is Sharlayan) or the Warrior of Light (whose only canonical backstory is "not from Eorzea", aka not Ishgardian). I think he was literally, foolishly, just thinking in terms of how to get through the next 5 seconds.