Blackrock Stew was the reward of the Dragon Food quest that required 2,000 loyalty points towards Bane Chosen and given out by the Bane Chosen Bounty Collector for 20 crystalline blackrock during the first event activated with Publish 66.2 in June 22, 2010.
The Blackrock Stew Recipe is the reward of the A Dish Best Served Cold quest that requires 5,000 loyalty points towards Ophidians and given out by Scalis the Ophidian Cook for a Bowl of Rotworm Stew, five Small Pieces of Blackrock and the arms of a Terathan Avenger. It is activated with Publish 69 in December 16, 2010 and its still active.
Bane Chosen was around for more than seven months and after Publish 69 (December 16), Bane Chosen attacked more than 15 times to different towns on each shard for more than a month. And they kept spawning for 24 hours during the invasions. The quest and the invasions were already announced here in Stratics and that was the perfect time to increase your loyalty rating.
I think it is a good reward for the ones who fought against Bane Chosen during the invasions. However, I also understand the ones who say they didn't have enough time to increase their loyalty rating:
The loyalty rating was capped at 2,500 until Publish 69. So, even if you had killed thousands of Bane Chosen soldiers, there was no way to increase it to 5,000 points before Publish 69 which is needed to take the quest. Also, if you had chosen the Bane side before Publish69, you had to kill 5,000 Bane soldiers to at least achieve neutral loyalty towards Ophidians (while the loyalty was capped at +2,500, it was also capped at -15,000 instead of -7,500) and 1,000 more to complete the quest. Nobody knew the recipe would be available only to Ophidian side and a good guess was pointing towards the Bane side because of the previous Dragon Food quest offered by Bane Chosen NPCs.