Since we now know all five factions in Heroes VI, I went trough creature lineup since Heroes I and there are some creatures that have appeared in all installments of Heroes and they are not included in newest:
6. Dragon (any kind but specially black, and yes I know that in Heroes I creature was named just Dragon)
Also there are factions that appeared in every part that are not included in Heroes VI.
3. Wizard/Academy (except in Heroes I)
There are also some iconic creatures that appeared in almost all Heroes and are missing now:
I guess that lost towns will appear in add-ons and that there are just 5 towns in vanilla because we will have 3 expansions with additional towns. That will probably also solve some of missing creatures issue, but current lineup gives me feeling of incompletion. Your thoughts?