The Hattisku are an aggressive Germanic tribe who range the lands known as Hattolandam, and are available to bolster the Suebian armies with tough veteran spearmen. Although somewhat low on hitpoints, their shields and their training allow them to function as a strong defensive unit, capable of holding ground whereso needed.
In The Wolf Among Lions, the Suebi can't recruit Hattisku unless they have first taken control of Hattolandam. Once that area is subjugated, a popup will appear, requesting the player to pay for their services, which will require some tribute. This popup will not appear until the next time when the Suebi take control of the territory again from a foreign power.