Sheiroballista - attacks in an area around the target with arrows (can be upgraded for a lot of money only in a neutral forge).
New ammunition for the ballista - incendiary charge - deals additional fire damage.
Magnonel - a siege weapon that fires a cluster of small stones in an area, can target units.
Trebuchet - an upgraded catapult, can only be upgraded in a neutral forge.
Fascines (bundles of wood) - an item purchased in a forge; when any unit approaches a wall, it gains the ability to cross the moat without any problems.
Bridge - an improved version of fascines for a wider moat (there should be one).
Ladder - can be placed against a wall, allowing units to climb over it.
Battering ram - heavily damages gates, but is slow.
Siege tower - can be placed against a wall, allowing units to climb over it; provides additional armor to those behind it.
Mantlet - a shield that absorbs attacks intended for the units behind it.