The contract of indemnity must specify that the loss is caused due to the action of the promisor himself, action of any other person which is not an event or accident, or any act beyond the control of the parties
Discharge by Variance in Terms of Contract (Sec. 133)
If any variation is made in the terms and conditions of the contract of guarantee without the consent of the surety, then the surety shall be released for the transactions that take place after such variations
Discharge by Release or Discharge of Principal Debtor (Sec. 134, 138)
The surety is discharged if the creditor enters into a fresh/new contract with the principal debtor by which the principal debtor is released, or does any act or omission in consequence of which the legal discharge of the principal debtor takes place