Magic Realms is an Iron's Spells and Spellbooks addon that aims to expand the amount of spellcasting mobs in the world, featuring hireable Mercenary NPCs.
Mercenaries are spellcasters that can be one of several Classes: Mage, Archer, Warrior or Assassin. Each Class has his owns strengths and weaknesses. These Mercenaries can level up from killing enemies, which will improve their stats.
To hire Mercenaries you will need to visit on of the Taverns they frequent in Plains biomes. There you can buy Contracts from the Tavernkeep, as well as maps to ISS structures.
Once you have established a Contract with a Mercenary, you will be able to right click them to change their equipment, view their combat stats and check what items they are carrying. Contracted Mercenaries can be ordered to follow you or to patrol a location by shift+right clicking them.
This mod doesn't only add mercenaries, but also other mobs to bring more magic to the world:
One such creature is the Chuchu, a slime which can absorb magic to take on its School.
Another addition are the Fizzles, sharply dressed creepers who have started appearing across the world. Be careful, for they don't explode like usual creepers…
In the Outer End Islands a group of enlightened Enderman have learnt Magic, being able to surpass their limitations and travel freely throughout the End. The members of this conclave call themselves Endermages.
From the depths of the overworld, a familiar undead has appeared, there are some who call him… Tim.
Magic Realms has Mercenary spellcasting compat with an expanding list of ISS addons, allowing Mage Mercenaries to specialize in new schools of magic and all Mercenaries to use new spells.
The Taverns themselves also have integration with several mods, if they are installed: