Looking at the in game maps, there are 13 side missions:  1 Kuwaq, 11 Paititi, 1 San Juan.

Every single website I go to only show 12 side missions: 1 kuwaq, 10 pai, 1 san juan.

So my question is:  Where in the world is #11 in paititi??

According to the Prima Guide: 

Kuwaq Yaku There is only 1
1. Blood Cries Out Giver: Victor (Look for lucia's missing nephews)

Hidden City There are 4
1. Skill Of The Player - Dice with the Dead Giver: Takiy ( Retrieve a child's lost toy )
2. Skill Of The Player - Cast Out Giver: Pisco ( Find and speak to five outcasts )
3. Draw Weight Heavily - the king's horn Giver: Uchu ( retrieve the king's horn )
4. Draw Weight Heavily - Hearts and Minds Giver: Uchu ( retreive the savior's amulet ) 

Return to Hidden City There are  6
1. In The Midnight Hour - Freedom mission giver - Poma ( Free 4 rebel prisoners )
2. In The Midnight Hour - A Particular Set Of Skills - Giver: Poma ( Find Colqui ) 
3. Knowledge of Evil - Ancient Studies Giver: Awil ( Decipher Three Cultist Murals )
4. Knowledge of Evil - Gods and Monsters Giver: Maya ( Rescue Awil ) 
5. Wolf at the door - Widow's Tears Giver: Businessman ( Solve Sumaq's Murder )
6. Collateral Damage - Stay Of Execution Giver: Etzli ( Free Haken From The Cult Brig )

San Juan There is only 1
1. How Sweat The Sound Giver: Guillermo ( Explore the mission )

So, Perhaps after finishing these 12 ( I have not yet done so ) I am currently in San Juan.  YOU can tell us what the 13th one is?

Looking at that list the only one missing is Finding the Savior Bow, which Uchu gives you before the "Point of no return" story mission.  which is last one I'm missing since Im in San Juan myself.

so I say that must the 11th and final mission in Paititi.

Hopefully the Good Samaritan unlocks after that mission, since Im 12 of 13 and achievement shows 75% of 8

Edited September 18, 20188 yr by Big Tyler 08

I'm not sure how the game counts the multi-part side quests. Does it go by the mission giver, the mission itself, sub-sections of each mission? FWIW, the map legend says "Mission Giver" for that symbol. Anyway, in case it might be helpful, here are screenshots of all the ones I have after reaching the 100% mark. 8 main missions with various sub-missions. I have no idea why it says "Cozumel" when I'm in Paititi.

 

Spoiler

 

 

Who knows lol.