Most Kobolds have the ability to shift one square as a minor action, but Dragon Shields have the extra ability to shift whenever a enemy moves toward or away from them. Because of this, the dragon shield Kobolds were able to move away from the rest of the party and surround Arlina.

Who just dropped a column of fire on Arlina and the kobolds?  find out on the next page.  By the way, that column of fire was actually a Scorching Blast, a first level wizard at-will ability. As such, it doesn't do much damage but it can hit several creatures within the blast radius.  Unfortunately, everyone in the blast gets hurt, friend and foe alike.