Fickle Water

Exterminate 12 Venomous Cnidaria and report your success to Sea Master on the Isle of Singing Water.

Water can be different: tender and affectionate, quiet and serene, icy and gloomy, roaring and fierce... Equally different creatures dwell in the depths of the sea. I am joyful about each, I cherish thoughts about each, I look after each. Just as a gardener roots out the weeds in a green meadow, I cleanse the clear water from filth as best I can. If you want to grasp the essence of water, you will help me in my laborious endeavor.
The sea is full of life, but there are those who, though endowed with life, only bring death to others. I am speaking about stingers whose venom can turn an elixir of life into that of death. Will you be strong enough to take care of that plague? If your answer is "yes," you will have my blessing.

All living beings are worthy of living, but what procures its life through others' deaths is worthy of nothing but dying...

I can hear words of gratitude in the swashing of water. Those words are being said by all sea creatures, both small and big. You have passed my trial with valor!