The 8th stage of the annual John Van Caneghem Tournament (2007).

Maybe he's not talking about those Hydras; there were supposedly 10 of them initially...

I remember clearly – 4 Hydras joined... near the swamp castle. But you needed a stronger army... i.e., you needed some monks or swordsmen... Basically, you just needed to build an optimal scheme for joining troops in terms of minimizing time... through trial and error... But it took a long time to figure it out, even with cheats.