Lord Nrsingha is one of the many form of Lord Vishnu, appearing in a half man-half lion form to protect His devotees from all kinds of harm.
Ugra Nrsinga is the Lord in His fierce form, ready to kill the demon Hiranyakasipu, who was harrassing his own son, Sri Prahlad.
Lord Nrisnga appeared from a pillar in the palace and killed Hiranyakasipu with His nails by taking him on his lap and thereby defeating the boon Hiranyakasipu had received from Lord Bhahma not to be killed by any weapon, not inside or outside, no human or animal, etc. In other words, he thought he was eternal. However, Lord Nrsingha appeared from a pillar, and killed him at the treshold of the door by using His nails as a weapon.
Mantra for Ugra Nrsingha:
Sri Nrisimha Maha-mantra
ugram viram maha-vishnum
jvalantam sarvato mukham
nrisimham bhishanam bhadram
mrityur mrityum namamy aham
"I bow down to Lord Narasimha who is ferocious and heroic like Lord Vishnu.
He is burning from every side. He is terrific, auspicious and
the death of death personified."
Length: 6.5 inches
Weight: 6lb 12.7oz