Steelhorns hero ability says: "Steelhorns can make one Melee attack when he declares a Run action. He must move in a straight line and end his movement after making the attack."

1- Can steelhorns attack any adjacent squares where he ends his movement or the target must be part of the straight line done running?

example: (x=Steelhorns movement, T=Target)

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2- If Steelhorn posses the Ring of Quickness:

Can he move 1 square to his left/right by using the extra MP from the ring and then use the RUN action to move on in a straight line (in an other direction) and then attack by using his ability?

Or to use the abilty all his movement for the turn must be in a straight line, and doesn't matter if the extra MP come from fatigue, ring or other?

example:

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Thank you

1) Yes, he may freely attack anything he can target. The attack itself is not restricted, just the movement.

2) No, he may move in a straight line only, regardless of what´s the source of the movement. As you  said, also fatigue-fuelled side-steps are not allowed if he wants to get his attack.

Thank you Parathion.