What is the first sublayer of layer 7 when dealing with continuous effects (layer 7a)?

In the context of Magic: The Gathering rules regarding continuous effects, layer 7 is specifically dedicated to effects that alter the power and toughness of creatures, and within layer 7, there are various sublayers that determine the order in which these effects are applied.

The first sublayer of layer 7, known as 7a, deals with continuous effects that modify a creature's power and toughness. This includes effects derived from character defining abilities (CDAs), which inherently alter the creature's stats based on specific rules.

CDA-based effects take precedence because they are fundamental and intrinsic to how the creature is defined. After CDAs, layer 7 will then apply other effects that either adjust power and toughness or set them to specific values.

Recognizing this hierarchy is crucial for correctly resolving scenarios where multiple effects may impact a creature simultaneously. Understanding that power/toughness-changing effects from CDAs are at the forefront of these changes helps clarify how subsequent modifications are layered and interact. Thus, those who study these rules must grasp the importance of layer and sublayer dynamics to effectively adjudicate and navigate gameplay situations that involve power and toughness adjustments.