Gem Knights are an older archetype introduced in Hidden Arsenal 5 back in 2011 that have recently received some support in Clash of Rebellions - most notably Gem Knight Lady Brilliant Diamond and Brilliant Fusion. This archetype focuses on Fusion Summoning recurring Fusion monsters and building card advantage and field presence by constantly adding back the Fusion Spell to the player's hand by removing a Gem Knight from the Graveyard. In the past, the deck was forced to run many non-effect monsters to summon their Fusion monsters, however the deck has now evolved to where this is only a minimal issue.
While this deck may not be tier one, it does have the ability to spam the field with powerful Fusion monsters and steal games from unexpecting opponents. While pure Gem Knights may not be a true competitive deck for some time, splashing certain Gem Knight cards into other decks may become a real trend.