Shield of Duty and Reason

The white member of a five-card cycle from an era enchanted with the idea of allied-color alliances: each Aura grants protection from the two colors that are its own allies. White sits next to blue and green on the wheel, so this points its shield at exactly that pair. The geometry is the design conceit, not personal grudge: the cycle traded the usual flexibility of single-color protection for a fixed, two-color slice you commit to in advance. The enchanted creature cannot be blocked by green or blue creatures, cannot be targeted by green or blue spells, and prevents all damage from green or blue sources, combat or otherwise; the package is one-mana evasion and partial shroud aimed at precisely two opponents and useless against the other two. Protection was the most efficient catch-all answer of its time, the lever you pulled to win a combat a creature could not otherwise survive or to slip a beater past a wall. This Aura is that lever pointed at a predetermined matchup. The cost is the cost every color-specific protection Aura pays: name the wrong pair and the card is a blank, a spent slot the opponent's deck simply never interacts with. It asks you to read which colors you will be fighting before a single card is on the table, then locks you into that read.