Currently through event only.
And also available in champions market now.
Skill
Covert Syphon
Reduces the chance of being hit and increases Attack Power by 15% for one round. Additional chance to reduce the Durability, Structures and Shields of enemies within 2 steps by 5% each turn. (Bart+Leo)
Note: The initial chance is the chance to trigger their ability when the total number of the related stats is 0. As the related stats increase, the chance to trigger commander ability will increase too. Click on the link to see a list and explanation of all Commander's Chance to Trigger Abilities.
The table shows the chance based on 500, 1000, 1500 and 1800 related stats.