Tuesday
 
Gem Knight received a lot of new Monsters and support in Hidden Arsenal 7, and we're looking at a Fusion Monster today.  Gem Knight Mater Diamond, who sort of strikes me as a Rainbow Dragon of Gem Knights (appropriate as Gem Knights are a supposed hybrid of Crystal Beasts and E-Heroes) is a Level 9 (great for Rank 9 XYZs) and an Earth attributed Rock Monster with 2900 attack 2500 defense.
 
2900 attack is low for Level 9, despite an easy Special Summon with three generic Gem Knights for Fusion.  It gains 100 attack for each Gem Monster in your Graveyard, so that puts you add at least 3200 given the Fusion itself.  Now as for what he does, he can remove a Level 7 or lower Gem Knight Fusion from your Graveyard to gain its name and effect(s) until the End Phase of the turn.
 
That's a wide array of Monsters, Gem Knights can fuse quickly, they aren't terrible swarmers, despite being not the strongest of Monsters.  It sucks the Monster removed has to be IN your Graveyard.  If you could remove from the Extra Deck instead, it might have some potential.  I'd use it in the Deck, and I'd like to see the Deck take off.  But until it does...

Ratings:

Traditional:    1/5 
Advanced:  2.5/5 
Art:  5/5 

Gem-Knights are all about special summoning Fusion monster, piercing, and raising monster attacks. Basically, your typical beat down deck on steroids. Gen-Knight Master Diamond is truly the Master of the Gem-Knights, with its 2900+ attack and the ability to copy a level 7 or lower Gem-Knight monster’s effect by banishing it from the graveyard. If you do not want to worry about your opponent activating cards or effects when you attack, banish Gem-Knight Citrine. If you want to inflict max damage, attack twice and do effect damage by banishing Gem-Knight Topaz.
 
What Gem-Knights do best is fusion summon, so getting fusion monsters in the grave can be done at a rather fast rate. Besides Polymerization and Fusion Gate, Gem-Knights have four highly effective fusion cards: Gem-Knight Fusion, Particle Fusion, Pyroxene Fusion, and Fragment Fusion. Gem-Knights have more fusion cards than any other archetype and a ton of monsters and support cards to rip though fusion monsters at an average of one per turn, so getting Master Diamond to the field and using its tool box effect, is not as difficult as it may first seem.
 
There are about 25 different Gem-Knight monster, Rescue Rabbit, and 8 other Fusion monsters that you can use to build one of many Gem-Knight decks. I would have to write a book to explain all of the different decks you can build. Suffice it to say, that fusion summoning is what Gem-Knights do, and it is very easy to search for the materials you need and to reuse them over and over again. If you are running a Gem-Knight deck, then you have to have the Master in you extra deck. Chances are that your two material fusion monsters will get the job done, but there will be times when Gem-Knight Master Diamond will be needed to win you a match.
 
Traditional: 2/5
Advanced: 3/5

Gem-Knight Master Diamond
Attribute- Earth
Types- Rock/Fusion/Effect
Level 9
3 “Gem-knight” monsters
Must first be Fusion Summoned. This card gains 100 ATK for each "Gem-" monster in your Graveyard. Once per turn: You can banish 1Level 7 or lower "Gem-Knight" Fusion Monster from your Graveyard; until the End Phase, this card's name and original effect become the same as that banished monster's.
ATK/2900 DEF/2500

Well, I don’t know much about Gem-Knight decks but this monster seems to be just okay. It takes 3 Gem-Knight monsters to summon it but it can copy other gem-knight fusion monster’s effects if they are in the graveyard. It also has nice Attack and Defense stats. All of those things aren’t bad but the cost of using 3 monsters to summon this monster seems like a large downside. It actually isn’t a bad monster but could’ve been a lot better. I might be wrong but this monster probably won’t do much to help Gem-Knight decks because it’s just too costly and not powerful enough to be worth using.

Advanced: 2/5
Traditional: 1/5
Art:5/5