Machine Beast (機獣; kijuu) is a family premiered in BS01. Almost all Machine Beast cards are White, and as the name suggests, are mechanical animals. Since Sword Eyes era, the family often sticks to the meta with its stability in both offence and defence. It receives strong cards almost every era, and accumulated to a great pool of cards for users to choose.
The first major Machine Beast deck was formed during Sword Eyes era, in which the "Dark" Spirits and Braves of White were dedicated to Machine Beast. Up till the beginning of the era, most Machine Beasts specify in blocking with strong blocking effects (e.g. the lineage of The MachineDeity Inphenit-Wols). And with cards like Wise-Monkey, they can go fro strong offence by turning the blocking effects to attack effects. The Ninetail lineage had led the family to new heights with strong cards like The BlackHeavenFox Nega-Ninetail. Later in the era, with the debut of strong white cards with Purple Rush like The DarkKingMachineBeast Darkness-Griffon, Jakou-Cat, and the Purple line-up of support like Bone-Dile and Nexuses like The Floating Island on the Mercury Sea, a Purple/White deck with The DarkKingMachineBeast Darkness-Griffon as the main finisher was established. The deck topped the meta throughout the Sword Eyes era and also the Ultimate era with its specialty in both draw power and defence, also with strong enough offence power. Even in nowadays, more than six years after its reign, the deck can still be seen in tournaments with different kinds of adjustments.
A surge of Machine Beast cards also happened during the God-King era. The family was shared between the colors Red and White, leading to mainly three variations of God-King decks largely owned by Machine Beasts, either led by The SheepTwelveGodKing Glorious-Sheep or The TigerTwelveGodKing Revol-Tiger. However, none of them relied heavily on the Machine Beast family, but instead, following the trend of that time, focused on the Ten Crown and God-King families. With the debut of The OxTwelveGodKing Avalanche-Bison, the pure white variant of the deck shifted to focus more on the family but eventually declined, losing in speed. The Tiger deck also stepped out of meta as the game developed further.
Around the end of Advent era, Machine Beast made a comeback with the "Machine Task Force" archetype that are both in the Armed Machine and Machine Beast families, under the lead of the X-Rare, The DarkStones MachineBeastDeity Fenrig, which has served as one of the most used countering Bursts in eras after (eventually limited to one copy per deck). Although the "Machine Task Force" archetype did not have a great impact on the environment as a deck, they later served as the support for Artemis's deck in the next era.
And as hinted, during the God Advent era, Machine Beast cards were made to support The Grandwalker Artemis, and formed the first deck that truly focuses on the family itself. The SacredMachineBeast Lightning-Ceryneia and The DarkKingMachineBeast Darkness-Griffon X were the main finishers, defeating the opponents by charging at them with multiple symbols in unblockable attacks, also with strong removals. Inheriting the traits from before, the deck has both strong offence and defence power, exemplified by Artemis herself. And the deck also has a strong "draw" power, despite being white, thanks to Godseeker-Negasbok and The DarkKingMachineBeast Darkness-Griffon X. The deck also inherited other strong mechanics from before, like "reveal and summon from deck" in both the Ultimate era and Advent era Machine Beasts. As for the connection with the "Machine Task Force" cards, The MachineTaskForce Shieldkong was actively in play, forming a combo with The CretaceousMarshal Lay-Saurer. Cards from the God-King era, like The SheepTwelveGodKing Glorious-Sheep and The OxTwelveGodKing Avalanche-Bison were also actively in play.
On the collaboration side, Type-3 Kiryu from the Godzilla series is consisted of cards majorly in the Machine Beast family. However, its severe lack of support kept it from gaining attentions from players.
In a general sense, Machine Beast is a long-lived family since the dawn of the game that gradually becomes one of the two major families that formed the core part of White. Throughout all eras, it keeps on receiving strong cards and support in all sort of forms. It has hence also earned sustainable popularity from among players.