Mirror Force
 
Was semi-limited 2.  Now is unlimited at 3.
 
This card has in recent months fallen out of favor for Dimensional Prison.  There are lots of monsters out there that either can't be destroyed or have a nasty effect once they are destroyed.  The Fire and Ice Hands for example.  I caught on really fast and swapped out my Mirror Force for D. Prison before the bandwagon caught on (hipster status confirmed).  Beelze is just so deadly if you don't have something like D.Prison to hit it, you're going to incur massive losses.  Mirror Force just doesn't cut it here.
 
But if Pendulum summoning becomes big and you're fighting off a swarm, maybe.  But I don't want to count any chickens until they hatch.  It's a bit sad, but Mirror Force has declined from a staple to an average card.  I guess the surprising part was how many years it took because Breaker TMW was chillin' at 3 for a while now.
 
I think at some point it may very well become big again.  For now, or at least the next few months, I don't see it. 
 
Again it's still a very good card.  It's a 1-for-1 at the least.  You have good destruction potential and can seriously mess up some decks.  At the very least, one Mirror Force can result in the opponent playing cautiously wondering if you have other Mirror Forces in your deck.
 
If you are a newer, casual or locals player and you want to slap a few Mirror Forces in your deck, that's perfectly fine.  It's quite a good card!  But when you're going to major events, use D. Prisons instead because you never know what cards you might be up against.
 
A timeless classic, a little down on its luck.  But with the way power creep is, I wouldn't be surprised to see a card that banishes all opponent's monsters when an attack is declared.
 
Traditional - 1.5
Advanced - 3.25

Mirror Force moving to 3 is a move that might seem too powerful at first glance, but within our current meta the move is justified. More powerful monsters continue to emerge which include effects preventing them from destruction, and as such, Mirror Force is often times not able to rid the field of threats. Mirror Force is still a powerful card with capabilities to + in card advantage if time correctly and against the proper field, however more often then not we are seeing fields filled with Fire and Ice Hand, which trigger nasty effects when destroyed. As such, Mirror Force isn't often times the best choice and could cause more harm than help in common scenarios. Moving in to the next format we will see many more fields with monsters such as El Shaddoll Midrash, which cannot be destroyed by effects at all.

For this reason, it is often more beneficial to use cards such as Dimensional Prison, which will banish the monsters, therefore circumventing monsters destruction protection or bypassing effects that activate by monsters that are destroyed and sent to the graveyard. Mirror Force is still a powerful option that against the right type of decks or fields, can clear the entire board and turn the tide of battle. However, in our current format and the format moving forward, there just isn't as much use for it as has been in the past and for that reason, the unlimiting of the card on the ban list is reasonable.

Ratings:

Traditional-1.5/5
Advanced-3/5
Mechanic Design-4/5 (Solid effect that encourages thoughtful planning in order gain advantage from the activation)
Art-4/5

Mirror Force

This is one of the newly Unlimited Battle Traps, but first for a brief history of this card:

This card was originally Limited and then due to it’s power was for a brief time Banned, then Limited again for quite some time, more recently it was Semi-Limited and now finally it’s Unlimited.

All of the above should serve to suggest how much of a diminishing impact this card has had on the game, a fact that personally I find quite disappointing, especially considering how much this card used to shape the game in the past.

Now onto it’s effect:

“When an opponent's monster declares an attack: Destroy all Attack position monsters your opponent controls.”

All of this is pretty simple really, your opponent declares an attack, you respond with this and hopefully, fingers crossed you say bye bye to you monster issue! A great bonus with this card is that it doesn’t “Target” your opponent’s monsters, it just destroys all of them in Attack position, ironically you could also destroy a face-down attack position monster with this also… Not that that is ever going to happen since Darkness Approaches is never likely to actually be played!!!

That it doesn’t “Target” is still a good redeeming factor for this card and that it can gain you some valuable +’s is also a good thing, and plusses are plusses… And don’t we all like to gain plusses?

Traditional: 1.0. This card in Traditional is simply outclassed and there is no actual benefit for you to be playing this unless you are playing a modified Traditional format Tournament, and even then, it is highly doubtful that you are going to play this card.

Advanced: 2.5. I really wish I could rate this higher, but the truth of the matter is, it’s not seeing hardly any play as it is currently, and even if you are playing this card, I highly doubt that you are going to consider playing 3.