I can only assume your thoughts on the soul of eternity
I think my favorite items in all of terraria are the items that combine like 10 things into one MEGA thing.
There's only a few off the top of my head, there's the obvious Zenith which obviously that thing is cool- it's a "post post post" game reward.
Terraspark boots, the triple balloon horshoe thing, Ankh Shield- even the cell phone and the associated parts (and its further upgrade)!
I LOVE having a reason to go around collecting tons of stuff to make a MEGA thing. Big fan when mods add yet more of that :)
(The spooky mod has multiple of these! Based on themed sets! Excitedly collecting!)