Going hand in hand with Shadow Mist yesterday, we have the card, which, almost every time, you will be adding to hand with Shadow Mist, in Mask Change. 
 
Mask Change is a fairly unique card. As I remember it described in the manga, it is "Essentially Fusion, but with one monster instead of two." While this grossly oversimplifies things, it is a rather valid comparison. Basically, you send a Hero from the field to the grave, and whatever attribute you sent, you special a Masked HERO from your Extra deck with that attribute. Note that this is not technically a Fusion Summon, so it bypasses certain cards(Non-Fusion Area, for example).
 
As for suitable Masked HERO's to summon off of this, there is at least one for every attribute, but the two standouts are Masked Hero Acid and Masked Hero Dark Law, mainly for their incredibly punishing effects and their attributes. Their attributes mean that they can be used alongside Shadow Mist and Bubbleman, the two best Hero's we have currently. There are obviously others, such as Koga(the third best IMO) and Dian, but they are far rarer to see.
 
As mentioned yesterday, this card can be searched by Shadow Mist, but also through Mask Charge, a great card for gaining advantage. This is one card that is hardly ever dead in multiples, because you can simply dodge effects using this. For example, lets say my opponent uses Snatch Steal, targeting my Dark Law. I can simply Change my Dark Law into another Dark Law, and let his Snatch Steal fizzle. Also, this can be used in order to bypass cards such as Skill Drain, as the monster that you Changed would no longer be on the field to be affected by Skill Drain, so his(mainly Acid's) effect would go off successfully.
 
A bit of a ruling note, you can use this card under Macro Cosmos and Dimensional Fissure, because it is not a cost to send the target to grave, it is part of the card's effect. Also, if your opponent chains Vanity's Emptiness against this card's activation, you will still send the monster as the card must resolve as much as possible.
 
Overall, one of the key factors of any Hero deck, and great at dodging effects and traps to boot.
 
Advanced:3.75/5

Mask Change...I suppose this is a relevant for a re-review with Heroes being solid again.  There are a million and one ways to Fusion Summon a Fusioned E-Hero Monster...most of which are crap, with things like Super Polymerization and Miracle Fusion being notable exceptions.  But Mask Change does HERO Fusion right, and the way it probably should have just been done in the beginning.  Being a Quickplay makes a very good card in this case very much better.  Mask Change is technically (at least initially) a -1.  But so quickly an easily bringing out a HERO Monster from the Extra Deck is incredible.  The only stipulation is the Monster you send to the Graveyard has to be on the Field and the one from the Extra Deck has to be the same attribute as the chosen monster sent to the Graveyard.  It's quick, it's efficient, and it's just damn good.  You use 3, period.
 
Rating: 4.75/5 
Art:  4/5