Elephants

[AntiochusIII]

War elephants were used in India and Southeast Asia for a long time. Both areas have long traditions of war elephants, and they were often used (at least in Southeast Asia) as "royal/nobility" mounts. There're also a lot of tradition about kings and princes "dueling" each other while riding elephant mounts. In fact, white elephants (a rarity) are sacred in several Southeast Asian countries.

However, despite their destructive effects and apparent strength and awe they have; the Mongols could easily defeat these war elephants once they knew how to scare them, and make the elephants run amok. Kublai's forces in Southeast Asia were fighting an old Burma kingdom, I think, and wrecked it completely (the old "Thai" and "Khmer" kingdoms were spared because they agreed to become the Khan's vassals - Vietnam, of course, was conquered - the northern part of it, at least) And of course, anyone who fought Indian forces in ancient times faced war elephants, and the Indians used them against each other often enough.