What if Herald was the tower version of Dragon?
Where we have different heralds, up till the 20 minute mark, that buff turrets instead of the champions.
EG. Red Herald: Rage: When attacking an anemy champion, gains X% attack speed for a short time. Blue Herald: Freeze: Towers have a slow Brown Herald: Fortify: Dmg reduction Green Herald: Emerald Spalsh: does Y% splash damage White Herald: Guardian: Grants a small shield to ally champions that refresh every minute.
The heralds won't stack.