Discussion about the Sanctuary faction.

Because the effects of "Aura of Radiance" remove all effects from the attacked creature during a normal attack.

As far as I remember, "Aura of Radiance" removes positive effects from all nearby enemies, which is not ideal, so at the very beginning of the battle, we cast "Time Stop" on them. Fortunately, the high initiative of the Sacred Kirin allows us to do this. But even better is "Tsunami" on the first turn. It immediately disables not only the "Aura of Radiance" but also all the main creatures. And then, after two turns, we apply "Time Stop" to the "Aura of Radiance". Later, we summon Earth Elementals, which use "Petrify" at the right time. Then Irina uses "Tranquility". The result: "Aura of Radiance" is no longer a problem for almost the entire battle. Of course, the enemy can correct the situation with "Dispel Magic," but they rarely do...

Why did you get disappointed with "Endurance"? Explain? Because I, on the contrary, wanted to try it.

"Endurance" is good for a warrior hero because they have access to the "Endurance III" skill, which provides a significant health bonus to the units. Having only the two previous levels of this skill, which Irina can acquire, I don't consider a significant advantage. Perhaps I'm wrong, but experience shows that there are more important abilities for the Fortress that you can spend your skill points on.

And describe in more detail how "Cloud of Smoke" is a key element of the Fortress strategy?

Oh, this is one of my favorite details. "Cloud of Smoke" stops almost all enemies when they cross it. It allows friendly units to act again (and this is not counted as a result of high morale, but as a full additional action without reducing movement range and damage). I think the benefit of this skill is clear.

Conclusions:
1. Protect the Sacred Kirin, preventing the enemy from destroying this unit;
2. Do not allow the opponent's troops to "pin down" the Sacred Kirin – their movement range should always be large;
3. Move the Sacred Kirin around the battlefield at full speed (not thoughtlessly, but calculating possible future actions of both the enemy and your own creatures, to immobilize the enemy and increase the mobility of your army – it's very nice when you can do both).

In fact, this is a specific advantage. At the beginning of the battle, the Sacred Kirin leaves a long "Cloud of Smoke" in front of the allies, and Kappa-Soyya takes advantage of this and instantly jumps to the large clusters of the enemy, dealing significant damage with "Power Jump"... And then, according to the plan. Although, to be honest, I prefer to wait for the Kappa-Soyya first. But that's not the point.

P.S. I remind you that the strategy being discussed is for the Tide Lord, a mage hero of the Fortress on the Path of Tears.

Added 23 minutes ago
And also: Mizu-Kami should be appreciated. Their "Spiritual Bond" not only shares all the joys and sorrows with the target unit but also endows it with "Pain Reflection" and "Protective Shell," allowing it to return 10% of the damage inflicted in melee combat to the attacker and reduce the damage received by 15%. Tip: try to connect Mizu-Kami and Sacred Kirin with these bonds. This will give a huge advantage: "Waves of Renewal" directed at one of the linked units will, of course, benefit both, meaning that the already quite resilient Mizu-Kami will extend their time on the battlefield, and therefore, "Spiritual Bond" will last longer, which means that the Sacred Kirin will not lose their additional protection and will continue to spread the "Cloud of Smoke" across the area. That's how it works. :p