“Wow! I'm glad that didn't gore me!”
“I wonder if the rings are an indication of age.”
“All that remains of a once great beast.”
“A TROPHY TO REMEMBER GOOD TIMES. LIKE WHEN YOU DIED”
“An amazingly large horn. I wonder if the nightmare helped fuel the growth.”
“That's a nice horn, eh.”
“A regrettable end, my old friend.”
“Can I add this tö my helmet?”
“It was an ordeal to get this.”
“I wonder, if ground up into a powder...”
The Guardian's Horn is an item dropped by Ancient Guardian, which is found in the Ruins. The horn can be used to craft a Houndius Shootius.
It is similar to the Deerclops Eyeball: it doesn't spoil, drains the same amount of Sanity when eaten, restores the same amount of Health and Hunger when eaten, and is dropped by a boss mob.
As it is a meat item, Pigs and Spiders will try to eat a Guardian's Horn, and Bunnymen will be hostile to players carrying it in their inventory.