What it does
Sand Tomb is a Ground-type physical move that deals damage on contact and then traps the target for 2 to 5 turns. While trapped, the target takes 1/16 of their max HP as end-of-turn damage each turn, and they can't voluntarily switch out.
The 1/16 chip per turn sounds small. Over 4-5 turns plus the initial hit, it adds up. More importantly, the opponent can't pivot away, which means they can't bring in a counter and they can't remove the damage by swapping to a full-HP partner. They're stuck.
Rapid Spin removes the trapping effect — that's the main out the opponent has.
Who runs it
Steelix runs Sand Tomb at 81%. It's a defensive Steel/Ground type with high physical Defense and a good type chart for absorbing hits. Its role is attrition — wearing opponents down, not bursting them. Sand Tomb fits: once it lands, the clock starts. The opponent has to deal with it or take damage every turn.
Some Steelix sets carry Sand Stream, which summons a sandstorm on entry. That means non-Rock, non-Steel, non-Ground opponents take 1/16 sandstorm chip on top of the 1/16 Sand Tomb chip — two passive damage sources at once against most of the opposing team.
How to use it
In doubles, pick your target carefully. Sand Tomb one of the two opponents, then let your partner go after the other. The trapped Pokémon can't swap in a counter — that removes one variable from your partner's turn.
While the target is trapped, keep pressuring with other moves. Steelix has Iron Head as a physical option and can combine trapping with passive damage and direct hits. Don't just sit there waiting for chip — keep threatening so the opponent can't freely pivot either member of their pair.
Steelix leaving the field ends the trap. In doubles this matters: if Steelix gets forced out, the locked opponent is free. Try to keep it in when Sand Tomb is active.
Tips & strategy
Rapid Spin breaks the trap. If the opponent has a Rapid Spin user, they can spin out of Sand Tomb on that same turn. Identify Rapid Spin users in team preview and plan around them — either KO them early or have your partner threaten them so they can't spin safely.
The trap duration is 2-5 turns at random. Expect roughly 3 turns on average, not 5. Build your plan around 3 turns of chip, and treat anything longer as a bonus.
Sand Tomb is a Ground-type move — it doesn't hit Flying-types, Pokémon in the air via Fly, or Pokémon with Levitate. Missing on your key trapping move wastes the entire setup. Check the opposing types before clicking.