Bran the Builder, the man who built the Wall, founded House Stark, and constructed Winterfell.
Lann the Clever, who founded House Lannister and took Casterly Rock from the Casterlys with nought but his wits.
The Grey King of the Iron Islands, who wed a mermaid and became king of the seas.
Symeon Star-Eyes, a blind knight who put star sapphires in his empty eye sockets.
The Age of Heroes is littered with legendary figures and their unbelievable acts, like Brandon Stark raising the giant Wall that guards (or rather, guarded) Westeros. But they're just that: legends, not facts, and there's as much reason to disbelieve them as there are think them true.
The prequel has a chance to shed a light on all of them and more, putting some of the most incredible figures and achievements on display, or breaking down the real, not-so-impressive truths behind them in true George R.R. Martin fashion, and seeing the likes of Bran the Builder or Serwyn of the Mirror Shield come to life, and learning what they actually did or didn't do (if ever they existed at all) should be fascinating for any fan of A Song of Ice and Fire.