I have a question about the yellow event card 'Of Giants and Dragons' from the Scepter of Kyros adventure variant.

It is a yellow event that gives all players a dragon rune. Is this a one-time only event? Or are all players to draw an additional dragon rune each turn until there is none left?

It is just a one time event. If it was meant to "trigger" every turn it would specifically say so.

Judd