The most famous of all Iberian units, the Hostatir is the Iberian answer to the Greek hoplite, and is the melee variant of the Scutanann infantry. Armed with a stout spear and an Iberian-style scutum, the Hostatir's primary job is to hold ground, and provide cover for the more lighter segments of your army. The large shields of the Hostatir make them fairly powerful especially in fights with other melee infantry, but rather slow in movement in comparison to the more lightly armoured Greek phalanx. Much later, you can also convert them into Hostatir Loricati , giving them an extra armour and attack boost to make them more effective in their job.
Take note however that powerful as they may be, Hostatir are considered as low-level professionals, and if faced with more powerful foes, partcularly the post-Marian legionaires of the Romans, they are liable of being destroyed in a sword brawl. In addition, their requiring Wealth in order to be recruited makes them very costly, so while they may be an awesome force especially against cavalry, it is unwise to recruit whole armies of them. Use these units the same way you normally use Hastati — by holding ground against enemies, and to create cover for your more lighter units should you see enemy cavalry on the horizon.