Might effectively buff the Talisman of Foresight, which I understand is already considered to be a strong artifact, but I guess that's not a fundamental issue.

Honestly, going big picture, I don't even really know why mimics got introduced in...Dungeons & Dragons, I guess? I assume that that's where they became a swords-and-sorcery staple. Like, it doesn't seem like they'd typically provide for a lot of opportunities to create interesting stories. Like, you can have a dragon or a human or something with a name and a story and all that, but a mimic is, well, a mimic. I guess maybe it could, if used very rarely, provide a surprise, but it just seems kinda limited.

kagis

Yeah, sounds like it was Dungeons & Dragons.

https://en.wikipedia.org/wiki/Mimic_(Dungeons_%26_Dragons)

An original creation for the game's artificial underground environment, this "iconic monster" looks like a treasure chest and is designed as a trap for unwary player characters.[1]

Advanced Dungeons & Dragons 1st edition

The mimic made its first appearance in the original Monster Manual (1977), by Gary Gygax. This book described mimics as "subterranean creatures which cannot stand the light of the sun.

It sounds like originally, Gary Gygax intended them to be slightly less-flat:

The Monster Manual mentions that there are two types of mimic encountered in the game. The slightly smaller version is more intelligent, and is generally friendly if offered food, usually telling a player character about what it has seen nearby. These creatures have their own language and can usually speak several other tongues. The book described the larger variety of mimic as a carnivorous creature called a "killer mimic". This creature does not speak, and will attack anything which is nearby.

It looks like somewhere between 1977 and 2024, that "friendly mimic" fell out of the Monster Manual, assuming that this is the entry:

https://www.dndbeyond.com/monsters/5195123-mimic