Magic Essentials: The Eternal Core Set: Mechanics
Focus:
You many cast this spell for its focus cost rather than pay its mana cost.
Used on 0 cards:
Represents how a planeswalker can concentrate on a single color and spell to reduce its cost.
Retconned:
This card shares its name with another card. A library cannot have more than four cards with the same name other than basic lands.
Used on 0 cards:
Restricted:
There can only be one card with this name in your library.
Used on 0 cards:
In card text or details pages, write the mechanic's code name (playtest name) between square brackets, like "[Crittercast]", "[Bushido 1]" or "[Delay 4 {2}{R}{R}]". It will be expanded to the mechanic's name plus reminder text, such as "Suspend 4 – 
. (Rather than cast this spell from your hand,...)"
To expand a mechanic's name but not its reminder text, include parentheses at the end of the square brackets: "[Crittercast()]", "[Delay 9 {R}()]".