Boy this was a tough one.
For those who don't know, "patience" is a huge map that puts you right in the middle of 7 enemy factions, all of whom have one-way portals that lead to your land within 1-2 turns from your city.
Needless to say this is a tough scenario and in challenging difficulty the first armies will be reaching your city by the end of the first week or the beginning of the second if you're lucky.

In this kind of scenario the first few weeks need to be perfectly calculated.
I played as arcane, with my starting hero being Ezduran.
The primary reason I chose arcane as the faction is the ziggurat building, which fully refreshed the mana of any hero in town.

Given the scenario I pivoted towards rushing ziggurat and other spell buildings so that I could turtle in town and survive the inevitable onslaught of armies marching for my capital.
This turned out to be quite a sound strategy, though I found that if two armies attacked my city in the same turn I'd face the second with whatever mana remained after the first. In those cases I would leave and let both armies fight over my city, then I would return the turn after and reclaim the city when the victor foolishly left with me only a file tiles away.

I chose Ezduran as my hero for his skills. Those of interest being mastery, with his speciality unit being goblin gunners/guards, which are effective behind city walls. Sorcery, which is handy when I have no restrictions beyond my maximum mana. Smithing, which allows me to acquire artefacts while being trapped baby sitting my city from being taken by invading armies, the archery minor skills was also of particular interest as it synergises very well with the goblin gunner speciality. Lastly engineering was useful for a defensive boost, but I didn't spec into it for some time. Bodyguards was of no use as I couldn't field another army until Ezduran was already overpowered.

In the first week I bought scouts and greedily hoovered up whatever free resources were lying around in my land, I also used them to increase mine output until we were invaded.
I did the usual thing of taking less risky fights with Ezduran to level him up without loosing too many oh-so-valuable early game units, with the exception being the obelisk as I wanted to find the buried treasure before getting invaded. It must be said that with arcane it is very difficult to build a substantial army for some time as the unit buildings are expensive.

My strategy largely consisted of turtling and fending off countless "impossible" armies until I was able to get some breathing room and reclaim all the resources that had been stolen by the various enemy factions.
Eventually Ezduran became very overpowered with tons of mana and spell power and I was able to recruit new heros and start to level them up, power levelling them with the academy.
After that the challenge was over. I had three overpowered heroes with limitless arcane power at their finger tips and the remaining factions were mopped up.

It took me many attempts to find the right build to overcome this challenge, and when I feel ready I will try again on hardcore, which I suspect will be much the same with the exception of more turtling.

Q: Why did i write this?
A: I just felt like it. It's been a journey trying to win this scenario. It's mostly for my own recollection but if you've read this far maybe you've found it interesting and about that I would be glad.