I'm a newbie at this, but I couldn't resist the urge to suggest something of my own. So, here I go.
My first suggestion is to take a feature from the fourth game, where you could leave the city with a group of creatures without a hero.
My second suggestion is to
introduce a new race.
"It is no secret that in every clan there are members whom nobody likes. And naturally, sooner or later, they are cast out from the friendly ranks of their people. Some for being provocative, some for a reason, but the fact remains.
For many years, the exiles wandered the world, becoming mercenaries, choosing the path of banditry, and occasionally standing up to protect the weak.
But one day, everything changed. It became known that the servants of Ranhull had erected a Temple to their ancient God on the island of Trunstar. The world was filled with rumors about the great treasures of this religious clan. The rulers of nearby lands decided to seize this easy prey. In response, the Adepts of Ranhull began to gather an army of mercenaries. Thousands of freedom-loving warriors began to arrive on the island of Trunstar. The islanders repelled the first attack, however, the will of the ancient God forever changed the lives of the defenders. Many mercenaries embraced the primitive faith, and for this, Ranhull—the god of elements—revealed to them the secret of ancient existence. The outcasts found a new Haven, and only now do they have a real chance to avenge their suffering."
Race name: OUTCASTS (or SERVANTS OF RANHULL, whichever you prefer)
Units:
1. MOUNTAIN DWARVES - Stocky little red-bearded fellows.
These dwarves were exiled because they didn't disclose a new gold vein and wanted to keep all the gold for themselves. They have full immunity to Earth magic.
Weapon - battle pick (or hammer).
1a. MASTER DWARVES - Chestnut hair, capable of summoning a small earthquake.
Weapon - war hammer (or axe, depending on 1).
1b. ACOLYTE DWARVES - These black-haired dwarves accepted the gift of the ancient god. Some parts of their bodies are covered in stone. They are capable of summoning a lava geyser and thereby turning the enemy to stone.
Weapon - double-edged battle axe.
2. NIGHT ELVES - they see well in the dark and are excellent at camouflage (similar to Warcraft elves). They were exiled for heinous murders. They have full immunity to poison.
Hair - long blonde, eyes green.
Weapon - forest bow.
2a. SHADOW ELVES - they live in complete harmony with nature. Sensitive to forest magic.
They can heal, but only their own kind, i.e., elves.
Appearance - black hair and yellow eyes.
Weapon - war bow, fires twice in a row.
2b. SERVANT ELVES - they use the gift of the ancients. Capable of controlling life-giving water. Summoning rains and destroying enemies using underground geysers.
Appearance - gray hair, blue eyes.
Weapon - sacred bow, they hold it horizontally and fire two arrows at once.
3. LONELY ORCS - orcs from the eastern forests. Exiled for their lack of desire to serve blood vendettas (very similar to the slave orcs from Warcraft). They have full immunity to Air magic.
Weapon - poison-dipped spear.
3a. DESERT ORCS - the wind is subject to these creatures. They can summon a destructive hurricane, tornado, or sandstorm.
(looking like the orcs from Lord of the Rings).
3b. FANATIC ORCS - through their fertile persistence in serving Ranhull, they earned the gift of controlling lightning. Electrical discharges constantly permeate their bodies. When closing in, they hit the enemy with a directed bolt of lightning, and enemies standing next to the target are hit by a chain charge. From a distance, they use magic to summon a celestial thunderstrike.
4. NORTHERN VAMPIRES - they will never resign themselves to their fate. Beautiful girls with a dark past. Upon attacking, they increase their number by 5% of the enemy's count. They have full immunity to Cold magic.
Weapon - two small sabers.
4a. CULT DEFENDERS - summon a snowstorm.
4b. GUARDIANS of Trunstar - their skin is covered in an icy crust. Upon attacking, the enemy is slowed. Icy shackles.
5. MERCENARIES - a man in a long hooded cloak. Carries a sword in a sash across his back.
They have full immunity to Fire magic.
5a. WARRIORS of RANHULL - the sword burns with divine flame. Can trigger a flame explosion.
5b. ADEPT WARRIORS - uses the divine gift, addresses the god with a prayer, and a fiery meteorite falls upon the enemy.
6. CHAOS MAGE - true servants of the ancient god. They have immunity to any magical effect, but low health. They attack from a distance.
Weapon - staff.
6a. WIZARD of LIGHT - when the time comes, a gifted chaos mage can become one. Fires a continuous solar beam that strikes everyone in its path, both strangers and allies. Blesses allies.
6b. SORCERER of DARKNESS - when the time comes, a talented chaos mage can become one. Upon attacking, he reads a spell and a suffocating veil of darkness arises around the enemy. Casts a curse on the opponent.
7. ANCIENT DRAGON - a one-headed hydra with wings, but cannot fly. Attacks from a distance with a fire breath. Magically summons an ice bolt.
7a. TWO-HEADED DRAGON - a two-headed winged hydra, it flies (similar to the chimera from Warcraft). One head attacks nearby with poison, and the second with cold (hitting adjacent units). Can summon celestial lightning with magic.
7b. THREE-HEADED DRAGON - (Zmey Gorynych) flies, attacks nearby. The attacked unit takes poison and fire damage, while neighboring enemies are slowed by cold.

Heroes of this race will ride zebras or camels. That's about it. However, I don't understand why there are no medusas, monsters, troglodytes, and naga in the fifth game? And why do the tribes of the east (goblins) ride mammoths instead of wolves or bulls?
But seriously, I would like the new race to be a nation of evil humans, something like bandits, and for the style to feature sultans and viziers, like in Assassin's Creed—West vs East.