Worm Tooth

Devourers only burrow through Corruption, so a Crimson world gives you no natural source at all. Two workarounds exist. The quick one is to craft Unholy Arrows out of Vertebra and throw the stack into Shimmer, which breaks them back down into their Corruption ingredients. The slow one has you speaking with the Dryad in Hardmode while standing in a Graveyard, which unlocks corrupt seeds in her stock, then grow a patch of Corruption big enough for Devourers to start spawning in it.

The arrow trick is worth remembering even in a Corruption world. It turns surplus ammo back into a material you would otherwise be grinding worms for.