I believe I have posted all I know about Undead tactics options... but here is small recap:
1.) Take Rina - let her in zombie form
2.) watch carefully for all artefacts that boosts undead - keep them, use them
3.) Try to sneak into Demonis ASAP - there are mostly the best undead units for purchase
4.) when already in demonis and you can't decide whom to take:
a) ancient vampires (bats) -> if you are lucky to get these, consider them as total MUST... you can even stack them in your backup slots (to not have to return to get them if you don't get sacrifice)
b) Dragons - great for hit'n'run tactics + can effectively collect battle chests (not fearing to be easily killed)
c) Any other vampires (if you can't get vampires (bats) take normal ones - you cans till transform them in battle)
d and e are optional -> you can go for skel archers if you don't mind losing some (if you don't go for 0-loss policy), necromancers (deal less damage, and can damage your own units, unless you don't mod them to "friendly fire 0" or my good old undead commander -> boosts morale
Keep in mind that one of your units may be green dragon later on, so prepare one of your units to be kicked out, early heads-up email in their mailbox will do
5.) Do not count too much on vampire steal life ability -> many units do not have "blood", have "no retaliation" ability, and your vamps can hit only once per round (do not have "furious" ability of demon or griffin...) also their damage is not as huge as the damage they can take
They are nice tanks, but still deserve some planning of you, dear general
6.) early on use ghosts, but watch out, especially on higher game diff. for over-running the max leadership cap, nasty nasty
7.) do not hesitate to take zombies in your army - they can take a lot of hits and deliver huge amount of damage as well, and have axes -> some artefacts work for them just better
9.) There is dwarven artefact that says "+30% damage from cold weapons" and it works for vampires as well
could be handy information
10.) If you feel sad that Rina has no weapon slots - download my MOD... you will find it in MOD section... somewhere
11.) watch out when fighting enemy undeads, prepare strategy more carefully or replace your units for the undead fights (dragons can do + ents, plants... dragons deliver huge fire damage - bad for deadies, ents and plants do not have blood - enemy ghosts/vamps won't ressurect/replenish
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