tDOT is powered by Stable Asset System
which is comprised 2 main functions:
Stable Swap - Enables highly efficient swap between native DOT and DOT derivatives
Stable Asset - Synthetic asset (tDOT) is minted and backed by standalone liquidity pools (native DOT and DOT derivatives)
With XCM, liquidity on Parachain can be used to mint tDOT on Acala then be transferred back to original chain to get unified.
tDOT has demonstrated the mechanism well during the aUSD incident. You can check here
to know how tDOT performed to keep the pool balanced.