Two questions about Steelhorns heroic feat

Move your Speed. During this movement, you may enter spaces occupied by monster figures and move those figures into an adjacent empty space (or closest empty space) of your choice.

1) Can Steelhorns move the monster back into the space Steelhorns just came from, essentially switching places with the monster.

2) The "closest empty space" confuses me a little. If two monsters large base monsters are in a 2x4 hallway, and Steelhorns pushes the first one back, does it get placed on the other side of the second monster? Sorry if that's confusing.

1) Yes, the space is now empty, meaning the figure can occupy the space.

2) Closest empty space literally means the closest space unoccupied by a figure. (For large monsters, they have to be able to expand to legally fit.) So you would push the large monster behind Steelhorns (Possibly the space he just came from, as the closest empty space would be one row behind you. (One space away, rather than four. [behind the other monster figure.])

1) Can Steelhorns move the monster back into the space Steelhorns just came from, essentially switching places with the monster.

Sure. The space Steelhorns came from must be empty if he has entered a new space, and it must be adjacent to the space he's now enetering, so it's a valid place to put the monster you're displacing.

If you want a thematic explanation, you can imagine Steelhorns bull's rushing the monster and flipping it over his back as he advances.

2) The "closest empty space" confuses me a little. If two monsters large base monsters are in a 2x4 hallway, and Steelhorns pushes the first one back, does it get placed on the other side of the second monster? Sorry if that's confusing.

You use the rules for "counting spaces" to determine which empty space is "closest" to the space the monster previously occupied and then put it there. In the case of large monsters, you would first "shrink" the monster into any of the spaces it previously occupied (not necessarily the space Steelhorns is moving into) and then count from there to find out where the closest empty space is. The Steelhorns player controls how the large monster shrinks as a result of this forced movement.

Once it arrives, it "expands" back. In this case, the "closest empty space" would implicitly mean "closest empty space that has room for the large monster to expand from" since large monsters may not stop moving in a space they can't legally expand out of, due to obstacles, walls or other figures.

FFG has clarified in the past that when "counting spaces" for an ability, Line of Sight is not required unless the ability specifically says that it is required. You can "count" through other figures, as only obstacles and walls/doors stop the counting process, and Steelhorns' ability does not say it requires LoS, therefore yes, if the "closest empty space" is on the other side of another monster, you could displace the first to the opposite side of the second as you move. Provided that was where the closest empty space was.

2) The "closest empty space" confuses me a little. If two monsters large base monsters are in a 2x4 hallway, and Steelhorns pushes the first one back, does it get placed on the other side of the second monster? Sorry if that's confusing.

You use the rules for "counting spaces" to determine which empty space is "closest" to the space the monster previously occupied and then put it there. In the case of large monsters, you would first "shrink" the monster into any of the spaces it previously occupied (not necessarily the space Steelhorns is moving into) and then count from there to find out where the closest empty space is. The Steelhorns player controls how the large monster shrinks as a result of this forced movement.

Once it arrives, it "expands" back. In this case, the "closest empty space" would implicitly mean "closest empty space that has room for the large monster to expand from" since large monsters may not stop moving in a space they can't legally expand out of, due to obstacles, walls or other figures.

I think I'd disagree slightly on the case of where you'd have to shrink the monster to. My guess (and this isn't a guarantee) is that when the ability says "adjacent" or "closest" that it is referring to the space that Steelhorns' entered which happened to contain a monster figure, not just any space the monster figure occupied. Granted, the ability is a bit vague, but this would also put things more in line with the clarification FFG made based on moving a figure with a weapon (the monster has to shrink into the targeted square)"

Granted, the ability is a bit vague, but this would also put things more in line with the clarification FFG made based on moving a figure with a weapon (the monster has to shrink into the targeted square)"

Oh, I was unaware of that particular clarification. In that case, I absolutely agree, the large monster would need to be "shrunken" into the space Steelhorns was entering before it gets displaced to the "closest empty space."