https://www.aonprd.com/MonsterDisplay.aspx?ItemName=Taniniver
If I will animate this creature dead into the bloody skeleton - will it retains it's diseased attacks? And if it will, what will be the DC of theese diseases?
Per basic rules skeletons lose all special attacks.
Special Attacks
A skeleton retains none of the base creature's special attacks.
Yes, but...
Special Qualities
A skeleton loses most special qualities of the base creature. It retains any extraordinary special qualities that improve its melee or ranged attacks.
For example, wolf skeleton retains trip special ability and gains +4 on trip, or zombie octopus retains grab and +4 on grapple.
Disease (Ex) is a special ability, not a special quality. If a creature has special qualities, they are listed under the SQ field of their Bestiary entry:
SQ: Any special qualities possessed by the creature.
The taniniver does not have any such qualities.
Thank you! Can you, please, give an example of special quality?
Sure thing!
Dryads have three of 'em--tree meld, wild empathy, and woodcraft.
An example of a special qualify that improves melee attacks would be Leviathan's powerful blows.
Interesting note: A lot of monsters (e.g., Selkie) have powerful blows without listing it in the SQ section. I'd interpret this to be an error, as Bestiary 4 and later have powerful blows listed in the Universal Monster Rules as a special quality. There may be other abilities like this, so use your judgment.
Edit: Also, though it goes without saying, if you're the GM in this equation, feel free to design your bloody skeletal taniniver with the disease ability anyway.
So, grab and trip are not kept by undead?
And if you say about powerful blows, what about dragons? Do they keep 1,5 STR bonus on damage of natural attacks(bite/tail slap)? I just think I was doing all wrong :)
What about BHOLE (https://www.aonprd.com/MonsterDisplay.aspx?ItemName=Bhole), that has no special quality about 1,5 STR bonus on natural attacks, but has such ability?