Activate Ashnod's Altar by sacrificing Rograkh, adding CC.
Rograkh dies, triggering Koll, returning Rograkh from your graveyard to your hand.
Cast Rograkh by paying 0.
Rograkh enters the battlefield, triggering Hero's Blade, attaching Hero's Blade to Rograkh.
Repeat.
This clever loop relies on Rograkh, Son of Rohgahh's cost of zero mana to immediately recast him whenever he leaves the battlefield. Ashnod's Altar provides the engine to sacrifice Rograkh for colorless mana, which simultaneously feeds your mana pool and triggers Koll, the Forgemaster. Because Hero's Blade automatically equips itself to Rograkh the moment he enters the battlefield as a legendary creature, Koll's condition is continually satisfied, returning Rograkh directly to your hand rather than the graveyard so the cycle can repeat indefinitely.