Rudra did not like the prospects of launching a frontal attack on Fort Magma. The fort was too heavily fortified and at a geographically superior position to be rushed in at blindly.
The way Rudra approached this was that , on the west side of the fort , was a small path , which merchants used to bring supplies to the fort. The western part faced away from the Aquahose territory on the east and Hazelgroove on the south.
That was the critical point for this fort. And for any average commander , if he/she could somehow disrupt the supply chain , then they would have effectively taken a step to further the seige.
However Rudra was no average strategist. His mind worked different , what Rudra was interested in was exactly using these merchants to poison half the army with poisoned rations.