In v0.8.9b, towers must be at specific distance away from each other.
You can observe this distance slightly, when your worker/peasant is about to place the new tower on the ground, there should be thin red circles around your existing towers.
And you must place your new towers outside these circles -> this is to prevent spawning dozens of towers near each other.
And nope, the new 0.8.9b is not completely documented, no fully revised manual.
That is why I even try to document some races and professions on this forum, till the documentation will be completed (In an extremely unreadable way: I play a game and comment on observed pros and cons)
Said that -> spells, skills, level-up, professions and races (with faction) are up to you to discover, sorry.
Despite the high level documentation is out there (main page of The Protectors and some are in MANUAL folder) none of the documentation is accurate, sorry.
When you create your hero, heed all the details about skills, stats.
Also know, that each 10 levels you will get one less skill point.
1~10: 5 points
11~20: 4 points
21~30: 3 points
Also extremely important (and entertaining) are the factions: one race offers 2 or 6 factions, each having a significant difference... and most importantly different Racial Synergy Bonus (one makes your units learn Assassination skill, other makes you to summon 10 dryads, or 15 Archons)
Also the army limit is set to 100 (but in campaign, it can be increased to 250)
Army points are now not exactly matching the size : for example small sized generals may consume 9 points (instead of 1)
Many many tweaks and differences and nearly nothing is properly documented, yet.