It is the strongest ranged unit. There is only one "person" in the unit, so damage taken does not affect the attack power of this unit. On the other hand, it is a very delicate unit that will quickly fall from enemy attacks. It has a respectable range from 3 to 6 fields and deals very high damage. It is worth improving it to level two as the maximum range will increase to 7 fields. Next, it gains an attack bonus, which will increases damage from 60 to as much as 110. It is an ideal siege and defense unit. A single attack of this unit can significantly weaken or even destroy your oppositition.
The big disadvantage of this unit is the inability to attack and move in the same turn, and the fact that it is able to move only one field (on roads and walls, however, can move as much as 3 fields). Moreover, it can only climb walls with special elevators. Therefore, the proper positioning of this unit is even more important than that of Crossbows. It will not be useful in missions where you attack on plains or forests. It will be spending too much time too far from the battle or it will slow down your attack tremendously. You can use a speed potion on it to compensate for this defect a bit. The cost of recruiting the first unit is not significant, but each subsequent unit costs increasingly astronomical sums. With 40 coins, its cost of teleportation is also very high. It is an expensive unit, but in this case price equals quality.