Mortar Tower is a first eraFireTower. Unlike typical towers, Mortar tower has no auto-cast offensive ability and relies on an activated ability, Mortar Attack, instead. Thus, this card is a poor choice for players who wish to leave an automated defense system behind while concentrating on other things, a role for which Makeshift Tower is suited.
However, this card is still very useful for players with good multi-tasking skills or are active in a defense role. Its attack can only be used in a small range from 30-40 meters (30-50 meters with Upgrade I), creating a thin ring in which the building's attack be aimed. Thus, learning what 30 meters translates to on screen will help with effective placement. It is also important to place them behind walls, cliffs, or other defensive structures that attackers will be likely to stop at. Alternatively, Crowd Control Cards can be used to halt aggressors in the targeting zone. Without these blocks, incoming creatures will head straight in for the Mortar and be too close to attack.
Finally, some words on the mortar attacks themselves. The attacks occurs with six bombings with good splash damage. Each bomb is not very precisely aimed, causing some reduction in damage potential. Also, placing two towers such that their target rings intersect at a pinch point in front of a wall or gate can be super effective at eliminating hordes of attackers, and helps to compensate for the inherent aiming "slop."
Activate to shoot 6 fire bombs that each deal 170 damage to enemies in a 10m radius around its target, up to 260 in total. Has a long range of 40m. Affects ground targets only. Reusable every 20 seconds.