Oracle Text

Whenever a creature deals damage to you, put a gold counter on it.

Each creature with a gold counter on it is a Wall in addition to its other creature types and has defender. (Those creatures can't attack.)

When Aurification leaves the battlefield, remove all gold counters from all creatures.

Card Rulings

10/1/2008 Aurification gives the creature type “Wall” to creatures with gold counters on them in addition to granting them defender.