The 3E "brilliant energy" weapon always gets pointed to as "like a lightsaber", but it's nothing like a lightsaber.
Brilliant energy: NO EFFECT ON INANIMATE MATERIAL.
Lightsaber: Cuts metal and stone.
That's mostly because a real lightsaber that cuts metal and stone is ridiculously useful. We had a DM that made the mistake of giving us one in 2e. It worked exactly like a lightsaber... for about three sessions. Then it basically functioned like a brilliant energy weapon. A real lightsaber is too useful.
"You find the outline of a door in the wall."
"I open the door."
"How do you try to open it?"
"We cut through the wall with the lightsaber."
"Uh... you won't be able to close it."
"Yep."
"We destroy the altar and the chalice."
"How?"
"I cut it to shreds with the lightsaber."
"There's a deep pit that extends down the passageway. You can't see the bottom of the pit, but you can can see that the passage continues about 50' away, but there's no obvious way there."
"OK, we carve a ledge we can walk on with the lightsaber."
"That's going to take awhile."
"Yep. We have time."
"Where do you put the rock you cut out?"
"Into the pit!"
"You find a steel chest."
"I search it for traps."
"There are no traps."
"I open it."
"The lid does not open."
"OK, we cut the hinges off with the lightsaber."
"There aren't any visible hinges."
"You might hit something inside."
"Yep. We're not going that deep. We cut the top inch of the chest off."
"The door is locked and appears to be held."
"We cut through it with the lightsaber."
"It's adamantine; that won't work."
"Yeah, but door frame is still stone, right? Or the frame is set in stone? So we cut the whole door out. Or just go through a wall."
Seriously. Being able to cut into anything with no effort solves so many adventuring problems. There are no longer any obstacles anymore. Everybody at the table figured it was a problem pretty quickly.