Captor of the Matriarch 

The way to chain an elephant is to start when it's a baby. You don't even need a chain- a strong rope will do. The baby elephant will struggle, but it will eventually realize that it can't break the rope and that it causes painful burns. The baby elephant learns not to struggle- it accepts that the limit of the rope/chain is permanent.
The elephant grows up to be the most powerful land mammal on earth, but the chain in its mind remains impossible to break.