Black Library/1.03.25

Undead
The Black Library is the final building needed to morph Undead units. With it, you can morph Slayer Knights into either Liches or Doom Knights. (Although Doom Knights still require every other morph related building to be present) Being linked to such powerful units, the Black Library should be built as soon as possible. But as the Black Library also produce the Undead Titan - Lord Bane, be sure to place it well to ensure that he doesn't get stuck in your base after he is produced. The Black Library seems to posses the same stats are the Altar of Shadows, including its hefty hit points. However, the Black Library is slightly larger, but still only average in size. As the building has endless spell researches that is limited only in the amount you can research at any one time, you may want to build a second Black Library to accelerate the amount of spells your Hero will learn - one researches Spell Research. the other Arcane Research. Of course, once you start to produce Lord Bane, then you may even go for a third Black Library.