What it does
Shed Tail cuts the user's current HP by half to create a Substitute, then forces the user to switch out. The Pokémon that comes in next enters the field with the Substitute already active. That incoming Pokémon doesn't use its own HP or action to set up the Substitute — it arrives protected.
In doubles, this is extremely difficult to play against. A standard anti-switch-in strategy involves using Fake Out to flinch the new arrival, or having both Pokémon focus the incoming target. With an active Substitute, Fake Out hits the Substitute, not the Pokémon. Spread fire hits the Substitute first. The switch-in gets a full free turn to act at maximum effectiveness, protected by a buffer it didn't have to spend a turn or HP to create.
The cost: the Shed Tail user takes 50% HP and leaves the field. The user needs enough HP and bulk to survive that cost while still being useful when it returns.
Who runs it
Orthworm (91% usage) is the dominant Shed Tail user in Champions. Base 145 Defense and Steel typing mean it can take a hit in the turn it uses Shed Tail, survive the 50% HP cost, and still have utility later. Its low Speed isn't an issue — it doesn't need to move first, just survive long enough to build and hand off the Substitute.
Heliolisk (30% usage) flips the Speed angle: base 109 Speed means Heliolisk often moves before opponents, building the Substitute and exiting before taking damage. The incoming partner gets a clean Substitute with no return fire on the setup turn.
How to use it
The timing question: which of your Pokémon is facing an unsafe switch-in situation? If your best attacker would walk into a Fake Out, two-targeting, or priority moves, Shed Tail front-loads a Substitute onto it so that threat is neutralized on arrival.
In a concrete doubles scenario: Orthworm leads, uses Shed Tail, exits, your Mega Evolution or setup sweeper enters with Substitute protection. First turn it can mega evolve, use Swords Dance, or fire its main attack without the Fake Out window that would normally exist.
Tips & strategy
Taunt blocks Shed Tail — it's a status move and Taunt shuts down non-attacking moves. If you expect Taunt on turn one, leading with Orthworm into a Taunt user is a poor outcome. Assess the opposing lead before committing.
The Substitute's HP is 1/4 of the user's maximum HP — it does not scale with current HP. A chipped Orthworm hands off the same-strength Substitute as a full-HP one.
The other Pokémon on your side of a doubles field acts independently — Shed Tail only forces the user out, not the partner. Both sides take their actions separately.