DCUO Boss - Zatanna
The first time I tried this zone at level 17, it didn't go very well so if at
all possible, get to level 18 before heading in.
Your first tough spot is going up against Lightkeeper Janis. She likes to stun and trap you. Be prepared with that Shift key to break out of the encasement. It works well to break the stun then use an ability to leap forward so you are spending less time running around and chasing after her each time she knocks you around.
Moving on from there, pick up the mission at the bookcase for a little extra easy experience. When you destroy each bookcase a group of mobs will spawn so make sure you aren't knee deep in other enemies before you tackle those.
In the final room, you release Eclipso and fight Zatanna. She is a pretty rough fight. There are orbs around the room that release shadowmen to assist in the fight. Use these one at a time throughout the fight. When Zatanna gets to about half health, she summons Etrigan who is also fairly tough. Break his stuns and keep a consistent flow of damage going. Finishing off Zatanna is also a matter of consistency. You should be on top of her at every second using your combos. Breaking her concentration and keeping her from casting any big spells is your best method of survival. Even if you are using the same one combo over and over again, just keep it going. When she manages to shove off, use a supercharged power then get right back at her. The key with Zatanna is to barrage her with constant combo attacks so she doesn't get the chance to damage you.