The empire grew under his son and successor Muhammad bin Tughluq, but the latter became notorious for ill-advised policy experiments such as shifting the capital from Delhi to Daulatabad
and introducing copper coins without effective regulation against
forgery. Tughluqi has as a result become synonym for brilliant if
stubborn eccentricity in the Urdu language.
After Muhammad bin Tughluq died, a collateral relative, Mahmud Ibn Muhammad, ruled for less than a month, until a cousin Feroz Shah Tughlaq
killed him and assumed the throne. His rule was somewhat weak
militarily, mainly because of inept army. After Feroz died in 1388, the
Tughlaq dynasty's power continued to fade, and no more able leaders came
to the throne; the dynasty was essentially over within 10 years.
The lowest point for the dynasty however came in 1398, when Turco-Mongol invader, Timur (Tamerlane)
defeated four armies of the Sultanate on December 15, 1398.
Subsequently the Sultan Mahmud Khan fled before Tamerlane entered Delhi
on December 18. For eight days Delhi was plundered, its population
massacred and over 100,000 war prisoners were killed as well.