Needs review
Source: Dark Sun 3

Description: In the heat of battle, weary and wounded soldiers retreat to be replaced by fresh, unwounded ones.

Prerequisites: Base Attack Bonus +3

You can swap positions with an ally within 5 ft. This is a move action that does not generate an attack of opportunity for you or your ally. You may not take a 5 ft. step in addition when rotating lines.

Special

A fighter may select Rotate Lines as one of his fighter bonus feats.