Describe the features of a blood clot.?

Depends: Depends on where the clot is and if it's in a vein, artery, or not in blood vessel at all (hematoma). Vein clots cause swelling and pain and may migrate to the lungs which can be lethal. Artery clots acutely impair the circulation: in the heart, it's a heat attack; in the brain it's a stroke; in the eye, it causes blindness, in the arm or leg, it's painful and could lead to amputation.