Blamish snail slime is used during the Hero's Quest to make an Oily Fishing Rod. Gerrant gives the player one for free after some dialogue, if they are currently engaged in the quest but have not completed it. It is used with a Harralander herb and water to get Blamish oil, granting 80 herblaw experience. After Hero's Quest is completed it cannot be obtained again.
If a player wants to obtain multiple Blamish snail slime to take advantage of the 80 herblaw experience gained by making Blamish oil, they may do so by using the Drop trick. The player may bank as many as they'd like and then continue to use the drop trick. Alternatively, a faster method of using this trick is to make the oil right besides Gerrant and drop it before talking to him again.