Avacyn's Collar, the Symbol of Her Church

Equipment usually adds; this one subtracts, and it never touches your own board. Attach it and the equipped creature stops attacking, stops blocking, loses the ability to transform, and has its activated abilities switched off entirely: a full lockdown wrapped in the flavor of shackling an angel. The absence of a standard Equip ability is the whole point. There is no way to bolt this onto a creature you control; the only way to move it is Shackle, a sorcery-speed cost that reattaches it to a creature you don't control for three mana. That reprices the effect from a set-and-forget prison into a leash you pay to relocate, chasing whichever enemy body has become the most dangerous. The "can't transform" clause is the tell for where the design came from: it exists to police double-faced permanents, the daybound and nightbound creatures and other flip cards that use transform as their escalation engine, clamping them before they can flip to their bigger side. Most disabling Equipment answers one creature and then sits there; the recurring sorcery-speed cost here is the discipline that keeps a repeatable removal-adjacent effect honest, since each move costs mana and cedes the current lockdown. It answers what static locks like Pacifism never could: not just a creature, but a creature that keeps changing which face it presents.