ToME: the Tales of Maj'Eyal

I'm relatively new to this game, have a few characters around level 40 and in the east. Been reading a bit in these forums and in game community chat, people talk about upgrading certain uniques to tier 5.

Is this some big secret or something I'll discover on my own just by playing through?

I'm holding onto those Spellblaze Remnants, they look pretty crappy now but apparently they are pretty boss if you get them up.

Spellblaze Remnants are the only upgradable item.
You have to destroy arcane artifacts with them to upgrade them.

that's not entirely true.
tiracai's maul has a gem slot, and while it is t2 by default, it will become of the tier of the gem in it if there is one.

Well, there's also the Wheel of Fate. I think Spellhunts are the only actually upgradeable artifact, but yeah, a couple others kind of can be as well.

oh, and then there is the telos staff that is in pieces.
and the 2 crystals that can be combined with equipment to create a crystal set? does that even count?

They're at tier 4 and still pretty crappy. What happens at tier 5 that makes them so coveted? It's like 8 armor, 4 defense, 10 mind power. Whoop de damn doo.

They get a different activate.