After Starting with the Retribution of Scyrah, you want to consider picking up some or all of the following models because you will use them in multiple armies.
What to Order
Heavy Arc Node with Reach
Phoenix

- PIP 35007 (Heavy Myrmidon Kit wit the sword and open fist)
The Phoenix's force field is even more durable than most retribution heavies because it can regenerate its field twice. It ca do so once with focus and again automatically during the Retribution player's turn.
Strike Force
Mage Hunter Strike Force with the Mage Hunter Commander Unit Attachment

- PIP 35014 (10 models)
- PIP 35015 (Unit Attachment)
Though Mage Hunters can do reasonably well without help, their Commander Unit Attachment takes them from good to awesome. He gives them the ability to use the Advance Deployment Ability and to fire Phantom Bolt shots, increasing their threat range to a ridiculous ranges.
The Dawnguard
Dawnguard Invictors

- PIP 35008 (10 models)
- PIP 35027 (unit attachment)
Invictors give you a tough unit with the Defensive Line Ability, a ranged attack, and the Flank Ability with your frontline myrmidons. Take Myrmidons with the Reach Ability to extend this capability.
Assassinate
Mage Hunter Assassin

The Mage Hunter Assassin adds a melee threat that simply must be dealt with. Most armies can't afford to let a high DEF model with the Weapon Master Ability charge with a 4" Reach Ability into their ranks.
The Original Angry Elf, Upgraded
Eiryss, Angel of Retribution

Epic Eiryss adds upkeep removal when you need it. Just be sure to keep her clear of your myrmidons.
Conclusion
Familiarize yourself with these Retribution of Scyrah tools, and you'll find a place for at least some of these models in many of your Angry Elf armies.