Best Secondary Commanders
Rise of Kingdoms Guide
When you level up any of your Commanders to level 20, they can then bring a secondary commander with them whenever they leave the City, so for gathering, fighting and even in the expedition matches, you can send a second commander to support your main one.
The role of the secondary commander is to bring their boosts into battle or into resource gathering.
It really depends on where you are utilising the secondary commander to decide as to which one is most appropriate for you to use at that moment.
Often commanders with the 'Support' tag are the ones most useful in a role as secondary commander.
Take for example, Tomoe Gozen, her Blood Sakura skill will boost the attack for all units by up to 30% when it is fully leveled up.
Another good commander to use as a secondary in battle would be Scipio Africanus, he can reduce the damage your troops take by up to 25% as well as increasing counter-attack damage by 25%
Joan of Arc is also a good commander to select in a support role in battle. Her Divine Revelation skill is a very powerful buff affecting both defense and offense of her own troops and nearby friendly forces. Her Maid of Orleans skill also gives good gathering boosts too.
Other good secondary commanders to help you gather include Gaius Marius, who can increase food, wood and stone gathering speeds
Best Support Commander - Offense
Joan of Arc
Best Support Commander - Gathering
Joan of Arc

I think in summary Joan of Arc is the best all-round secondary commander in the game, but there is only one of her - so use wisely!
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