Idea I had for the next big game mechanic to focus a series on: Synthesis.
How it works: A Synthesis card (now a universal sub-type for Monsters, Spells, and Traps; not to be confused with
this) starts in your Extra Deck. To Summon (for Monsters) or activate (for Spells/Traps), the listed Synthesis Materials are sent from the Graveyard to the Synthesis Zone (a new spot on the board; Synthesized cards are not Banished, and while effects using cards in this Zone will say "you control," they are not on the field either) face-down. At this point, they are no longer treated as cards, but as Synthesis Material; this will play into various card effects.
For Synthesis Monsters, they're treated as having a Level and a Rank simultaneously, with the Level/Rank Stars centered on the card. A Synthesis Summon will require 2 or more monsters from your Graveyard with a Level equal to its Level/Rank. For example, summoning a Lv/Rk 3 Synthesis Monster can be accomplished with Tour Guide and Sangan in your Graveyard.
For Synthesis Spells/Traps, activation timing is the same as per its usual printing: a Normal Synthesis Spell Card can only be activated during your Main Phase. The Synthesis Materials for activation will generally be 2 or more cards of the same type (Spells for Synthesis Spells, Traps for Synthesis Traps).
Of important note: A card cannot be used as Synthesis Material in the same turn it's sent to the Graveyard. So, for example, no using Future Fusion (yes I know it's banned, shut up) to dump 5 Level 8 Dragons to the Graveyard for 5GD and then trying bring out 2 Lv/Rk 8 Synthesis Monsters. Also, Extra Deck cards cannot be used as Synthesis Material no matter what.
Also: Regardless of it being Spell, Trap, or Monster, a Synthesis Card has a turquoise background.
BLAZE SABER
FIRE/LvRk 4/2000 ATK/1700 DEF
Warrior/Synthesis/Effect
2 Level 4 monsters
This card gains 100 ATK for each Synthesis Material you control. Once per turn: you can return 2 Synthesis Material to the bottom of the Deck; deal 300 damage to your opponent.
POT OF NARCISSISM
Normal Spell/Synthesis
3 Normal Spell Cards
Draw 2 cards.
SWORDS OF ALCHEMIC FORCE
Continuous Trap/Synthesis
2 Trap Cards
Your opponent cannot attack or activate the effects of Monster Cards on the field while you control this card. During your 3rd Standby Phase after activating this card: destroy it and return 2 Synthesis Material you control to the bottom of the Deck.
OBLIVION'S JUDGMENT
Counter Trap/Synthesis
3 Trap Cards
Pay half your Life Points and return all Synthesis Material you control to the bottom of the Deck. Negate the activation and effect of a card or the Summon of a monster and banish it face-down.
100
100
200
