If you click on the Hellforge and have Mephisto’s Soulstone in your inv/cube/stash, the stone will appear on the Hellforge. (It must first be identified in early versions of Diablo II.) Souls are released from the shattered Soulstone. You must kill him to make him drop the Hellforge Hammer, which you should then equip. At the Hellforge you’ll find Hephasto the Armorer, a SuperUnique monster. This is the forge Izual was attacking to prevent the completion of Shadowfang when he was captured, in the Diablo mythology. You must destroy the Soulstone you got from Mephisto on the Hellforge, a blacksmith’s forge in Hell.

In D2X it’s much easier and has a better quest reward. It was frequently skipped in v1.08 and earlier since Hephasto was so fierce.

Quest Priority: Optional quest, but a good reward.

The rune is randomly selected from within the following ranges: The Expansion adds one dropped Rune per game.

Reward: Smashing Mephisto’s Soul Stone on the Hellforge drops four random type gems, one normal, two flawless, one perfect per player finishing the quest.

Location: Hellforge in the River of Flame.

Triggered by: Completing Quest One, or entering the River of Flame.

Hephasto the Hellsmith is always found near the Hellforge, and he must be defeated and his hammer taken to complete the Hell’s Forge quest.

Its location changes, but it is always found at the tip of a peninsula. The Hellforge is an object located in the River of Flame in Act Four.

3.2 Activation (Mephisto’s soulstone wasn’t picked up).

Where is the hellforge in diablo 2