Persia rewards aggressive early conquest with a self-healing military and a real economic payoff for every civilization whose territory you take a Settlement from.
"Hamarana Council" gives Infantry Units increased Combat Strength when attacking, and Army Commanders start with a free Promotion. Its Antiquity Age Apex tier adds increased Combat Strength for units fighting in enemy territory, plus increased Culture and Gold for every different civilization you've captured a Settlement from — genuinely rewarding conquering broadly rather than just conquering a lot.
The Immortal is a unique Infantry unit that heals for a set amount after defeating an enemy unit, letting an aggressive Persian army sustain a campaign without constant retreats to heal. The Hazarapatis is a unique Commander that starts with the Initiative Promotion, letting units move immediately after unpacking from the Commander instead of losing a turn to it.
The Pairidaeza is a unique Improvement generating Culture and Gold, with increased healing for Military units stationed in a Settlement that has one. It's Ageless, doesn't remove existing Warehouse bonuses on the tile, but must be placed on an existing Improvement and can't be adjacent to another Pairidaeza. The associated Wonder, the Gate of All Nations, adds Happiness and War Support and must be placed adjacent to a District.