I played this with someone and noticed a few things that would make the game a bit smoother.
My natural reaction was placing items on the graves/bookshelves the same way you give items to other Heroes or sell them to shops.
Some quests/hidden events can't be activated because of the need to put items into the inventory of enemy objects. With no clue at all how to do this, it felt kinda bad there was more to be explored but impossible to reach due to this mistake. It can easily be fixed by making everything you want the player to put an item in be an ally of the player. If you want it not getting attacked by enemies of the player take it easy and make the objects Neutral Passive.
Ability buttons turn green when you're hit by Maedros or when you press F10 or the like.
Fix this with DISbuttons.
There was a very annoying bug where a quest triggers twice when the 2 players walk into the area on different times.
Fix this with putting
Trigger - Turn off <this trigger>
at the start of the entering region trigger.
Also, when I press Esc to skip a cinematic, I have to wait for the trigger to finish before all units are unpaused again.
Fix this with putting
Unit - Unpause all units
in the trigger where you exit the cinematic.
Surely having no regen was quite exciting, having to watch your HP in fights. And I get that you're undead and all; ''healing'' isn't really a thing among them, but waiting tens of thousends of minutes for your only way of recovering health to get off cooldown is abhorrent. The Undead in the casual game have Blight they can heal on. Maybe an idea to use that instead of a Fountain?
I liked the fighting part and the skills, but the walking is terrible. It takes a really, REALLY long time to get from point to point. Place some teleporters at important locations to avoid unnecessary agitation and waiting.
Still some fixes required for the things others mentioned earlier like fr0ggE summed up. Other than that, it was kind of interesting to play and I like the setting and theme.
If you apply these changes I'd even recommend it to other people if only they would play War3 :< :<
Good work!