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.
The Wall of Steel is a boss that can be spawned in the Underworld by letting a Mechanical Guide Doll fall into. lava after Hardmode has been unlocked. It is a stronger, mechanical version of the Wall of Flesh. Once the doll has fallen into lava, the Guide will die, and the Wall of Steel will awaken.