Thank you for your kind words! Undertale was a main inspiration :) (also there is a game called Don't Look Back which inspired the art style)
Spoilers Ahead
You can kill the snail with Dark Fire, which you obtain by finishing the Warlock quest. Alternatively, there is a secret "Healing Cucumber" found in a secret area in the forest, which you can use to heal the snail instead. Also you can just avoid it :P you don't need to "pass" it to complete the game, but you already know that :P