Wrapped
A Kraken tentacle has one of your blocks in its grip. You can't match it or move it, and cracks spread over it as the grip tightens, until the tentacle crushes the block outright. Match right beside it and the tentacle lets go, though it will reach back for another. Kill the tentacle and the block is yours again for good.
In detail
The strictest lock. A wrapped block cannot be matched or swapped, and it is anchored, so free blocks fall around it rather than moving it. The crush timer is the tentacle's grab interval, about 10 seconds, and cracks spread across the block as it runs down. At zero the tentacle shatters the block and the cell clears, earning no chain. A match orthogonally beside it breaks the grip, though the tentacle reaches back for another soon after. Killing the tentacle frees the block for good, and ability clears such as Leváteinn's Edge or Chain Lightning free it too.
More in glossary
From the current development build. Content and balance may change before release. This public reference includes discoveries and does not reflect your personal unlocks.