Sense of to exist, be present is attested from c.1300. Meaning to pay for as a treat is from 1821. Phrase stands to reason (1620) is from earlier stands (is constant) with reason. Phrase stand pat is originally from poker (1882); stand down in.
In Expert Mode, Wall of Flesh is seen to be significantly faster than his prior speed, posing map navigating harder as the players are demanded to plan out their routes fasters. In addition, getting pulled by his tongue will inflict additional damage to the player, possibly killing a weakened player.
Mining Obsidian and Hellstone Bars for Crafting. Mining Hellstone with only an Obsidian Skull can be tedious. The potion makes things much faster. You can do it without either of them, but it's a time-consuming process. One of the key aspects of preparing to go to Hard Mode is the defeat of the Wall of Flesh.