The Flail Elephant has a rapid siege attack, and a massive ranged resistance and can demolish buildings in seconds, but is fairly poor in combat, largely due to its low speed and vulnerability to heavy infantry and ranged cavalry.
Flail Elephants are very effective at taking out buildings such as Forts and Town Centers incredibly quickly, sometimes before the enemy is able to react. They are capable of dealing with artillery extremely effectively, if they are able to reach it; they are the only Indian heavy cavalry that has a multiplier against cannon and all of them share the trait of having low base damage. Thus, Flail Elephants can somewhat fill this weakness.
After "Professional Handlers" has been shipped, Flail Elephants become very population-effective damage sponges. As Mahout Lancers are quite easy to focus down (as well as expensive), and Sowars are quite fragile, Flail Elephants can offer a middle ground option to soak up ranged infantry fire to protect a player's ranged units. This is especially important for the Indians because they lack a massable artillery piece. Flail Elephants don't do a large amount of damage, but can supplement armies as a tank unit and anti-artillery without taking too much population space.
Inspires all nearby Flail Elephants. Powerful Elephant from India that swings a mace. Good against buildings.
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—In-game description
The Mansabdar Flail Elephant is a stronger version of the Flail Elephant that can be trained from the Charminar Gate wonder. As a Mansabdar unit, the Mansabdar Flail Elephant has twice the hit points of a Flail Elephant and Imperial Service that increases the hit points and attack of nearby Flail Elephants, but are two times more expensive.
Flail Elephants cost 3 population, have 10 attack, and give 25 XP when killed.
Mansabdar Flail Elephants cost 6 population, have 10 attack, and give 50 XP when trained or killed. With Update 20322, Mansabdar Flail Elephants cost 3 population.
The Flail Elephant is the only hand siege unit, together with the Ram, and they are also the only two units with a siege RoF of 1.5.
Besides the aura underneath it, the Mansabdar and Honor/Exalted Flail Elephant can be difficult to distinguish due to having the same identical features.
The Dravidian Martial Arts card boosts their siege damage by 15%, not just their melee attack.
Although there are few accounts to substantiate its existence, the flail elephant was said to have been a cavalry and siege unit fielded with the early armies of Sri Lanka. It would enter battle whirling a heavy iron chain that had been affixed to its trunk, becoming both a terrifying and entirely unapproachable force.