> Also why have so many of the unique artifacts got drawbacks?
Because I bought the rpg Powers and Perils sometimes in the 80's!
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OK, that was not entirely fair!
Named Items (unique artifacts) in that game came with a drawback. It could be anything from not being usable unless under certain circumstances to lethal effects like cunsuming the bearers will or life force.
In literature the same phenomenon is also not unheard of. The One Ring and Stormbringer are clearly not beneficial to the bearer.
All in all I find it fitting and fun, and it makes it more difficult to make an uber SC or something similar. I actually dislike powerful items without drawbacks. Too easy to make winner strategies that way. Less fun thematically. Less fun incidents with insane commanders