Under the layer system (CR 613), continuous effects are applied in a specific order. Layer 4 is where type-changing effects are applied — this includes effects that change, add, or remove supertypes, card types, subtypes (such as creature types), and other type-related characteristics.
CR 613.1d defines Layer 4 explicitly: 'Layer 4: Type-changing effects are applied. These include effects that change an object's card type, subtype, and/or supertype.' This means if an effect says a creature 'is a Human' or 'loses all creature types and becomes a Zombie,' that modification is locked in at Layer 4.
It's important to understand that Layer 4 is processed after Layers 1–3 (copy effects, control-changing effects, and text-changing effects), but before Layer 5 (color-changing effects) and Layers 6–7 (ability and power/toughness changes). The order matters when multiple effects interact.
Concrete example: You control a Shapeshifter with the Changeling ability (it is every creature type). Your opponent casts Lignify, which makes the creature lose all abilities and become a Treefolk. Both Changeling (which sets types in Layer 4) and Lignify's type-setting effect are applied in Layer 4. Since Lignify's effect specifically overrides the creature's types and Changeling is removed in Layer 6, the creature ends up being only a Treefolk — not every type.
If multiple type-changing effects apply at Layer 4, they are ordered by timestamp (CR 613.7a) or dependency (CR 613.8), meaning the most recently applied effect generally takes precedence unless dependency rules dictate otherwise.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.