None of which are easy to utilise. No one knows how the mourning happened or how to utilise it. Argonnessan isn't one of the nations in Khorvaire, and while it could probably give the FR a run for its money in sheer power, it actively avoids expanding its influence by conquest.Eberron has the mourning and ancient dragons that control time and space as well as a literal monster empire. Let's not pretend that its theme of wide magic doesn't mean there aren't literal world-enders walking around, or that they can't figure out how to make an orbital barrage of meteor swarm.
...
And what Eberron calls The Mourning, FR calls a Tuesday. ...

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.