Next time my full group is together for DnD i will be charged with DMing. The group is currently part of the elven army and have been told that they are laying siege to a fortress that they built, and then was captured by undead and shard-kai. The Elves built the fortress so that it wouldn't be destroyed by the undead. It was suppose to be impenetrable.
Sounds like there's a story there...So how did the undead and shadar-Kai overrun the "impenetrable" fortress?
How does one run a battle like this? any hints and tips you can give. It needs to be more then just battle-battle-battle-battle. What are some objectives that they can fulfill during the course of the battle to determine weather they win or lose the battle?
It depends on how the fortress is designed. Many fortresses would have an outer and inner bailey, so the undead could fall back to the inner bailey if the PCs are winning...or the wily shadar-Kai could let a headstrong elven prince charge into the inner bailey then shut the gates separating his unit from the rest of the army fighting in the outer bailey.
Here are some cool non-combat things you might include:
* A necro-gem (puzzle) which must be destroyed/disarmed to prevent the elven army's dead from rising as undead
* Tormented spirits who were hung off parapets and cursed by Lich ask intensely personal riddles of those who approach - killing all who fail with their deadly visage/voice
* An elven agent is hidden in the undead court (either a good-aligned undead, a living creature "allied" with the shadar-Kai, or a Mage disguised as undead) who the PCs need to reach for urgent intel
* Some of the animated undead possess a multi-part clue that their bodies were buried with/wearing (e.g. seven seals which combine to form Great Seal of the fortress)
* Negotiating for military aid from an order of paladins who historically had bad relations with the "pagan" elves
* Investigating a potential necromancer spy among the elves
* Interrogating a shadar-kai captive or defector who is extremely standoffish