What it does
Mummy works passively: the moment any Pokémon hits Cofagrigus with a contact move, that attacker's ability is instantly overwritten with Mummy. No action required from Cofagrigus, no turn spent. It just happens on impact.
The replacement is permanent until the affected Pokémon switches out. Non-contact moves — Earthquake, Flamethrower, most spread moves — trigger nothing. But Close Combat, Drain Punch, U-turn, Wild Charge: all contact, all trigger.
The abilities hurt most by this are the ones that function as the whole reason the Pokémon is on the team. Speed Boost gone means no more escalating priority. Mold Breaker gone means it can no longer bypass Levitate or other protective abilities. Guts gone means the status condition on it now just hurts instead of helping. Huge Power or Pure Power gone means the damage output drops by roughly half.
Cofagrigus itself is unaffected — it is the source, not the target.
Who runs it
Cofagrigus is the only Champions-viable carrier with Mummy as its main competitive ability. Its defensive profile is what makes the trap work: solid physical bulk, Ghost typing that immunizes it to Fighting-type contact moves (Close Combat, Drain Punch), and enough staying power to weather the hit it needs to receive. It is not purely passive — Nasty Plot into Shadow Ball is a real offensive threat, and Will-O-Wisp compounds the physical attacker problem on top of Mummy.
How to use it
The plan is to identify which opposing physical attacker depends most on its ability, then route Cofagrigus in front of it. You are not waiting to get hit — you are positioning so the opponent's best move is to send in the contact attacker, and then it pays the price.
Pair Will-O-Wisp with the Mummy trigger for maximum effect: burn first to halve physical damage, then let the contact move overwrite the ability. The physical core goes from threatening to nearly irrelevant in two steps.
The Mummy effect clears if the affected Pokémon switches out, so squeeze the value while it is still in play. If the opponent pivots it out immediately, that is still a turn won — they spent their switch to escape rather than attack.
Tips & strategy
Prioritize these ability targets: Speed Boost, Mold Breaker, Huge Power, Pure Power, Guts, Contrary. Removing any of these from the attacker that relies on it is a meaningful exchange.
You can use Cofagrigus as a one-time ability eraser — switch it in on the predicted contact move, let the trigger fire, then immediately swap to your actual win condition. Trading one switch-in opportunity for a permanent ability removal on the opposing core is usually the right call.
In doubles, Mummy's reach is limited. Most strong doubles moves are spread attacks or non-contact, so the trigger does not come up as naturally. Singles is where the trap setup pays off most reliably.