The Bite-Sized series of articles is meant to take the most powerful cards in Dominion and give a short explanation of what makes them powerful.
At first glance, Overlord might just seem like an expensive Band of Misfits, which isn’t a very powerful card, but Overlord has a couple of use cases that push it up to one of the best cards in the game.
The first is opening with an Overlord. You can have access to a $5 card, even if you didn’t open with a 5/2, along with whatever else you can afford on your first turn, if you just buy an Overlord on your second turn. This is strongest when there is a $5 card that trashes cards or attacks your opponent, because these effects can be meaningful even if you’re in debt. If you can open with the card otherwise, or if your only $5 options for Overlord are cards that make money, Overlord openings aren’t nearly as good.
Overlord’s flexibility is not to be ignored, though. Its role can change as the game progresses, so you may play it as a trasher or junker early on and then something else when that’s no longer useful — in these cases you may even consider opening with an Overlord if the trasher or junker costs less than $5. The flexibility is stronger with Overlord than Band of Misfits simply because you will have more options to choose from, and those options are usually stronger because $5 cards are significantly more powerful than $4 cards.