Key 7909 
This key can be found from a pile of bones inside a tree on the Isle of Ada.
To enter the tree, you must wait until a crack appears on the ground on the floor above it
Here:
Hole: (Active sometimes not always)
Pile of bones with the key inside:
Then you can use the key here to open the gate
Key 7772 
Can be obtained from Brass-Shod Chests on the Isle of Ada.
There are 13 Brass-Shod Chests located around the Isle of Ada (Tibia), which can be looted every 20 hours, with some requiring specific keys or access times, such as the harpy nest (night only) or the mine (Key 7909).
Locations of the 13 Brass-Shod Chests on Isle of Ada include:
- Bear Area: North, requiring levitate.
- Adlerauge: Near the boss area.
- Herald: Near the herald area.
- Tree: Inside, accessible with a Secret Service tool on a crack in the floor above.
- Harpy Nest: Accessible only at night, roughly XX:15 to XX:45.
- East Boat: Near the boat.
- Mines: Behind a gate requiring Key 7909.
- South of Bastion: Near the structure.
- Planks: Near wooden structures.
- Bedroom: Inside the main building.
- Church: Inside the religious structure.
- Gold Hoard: Near treasure piles.
- Underground: In the lower levels.
- Stag Bastion (5+ chests): Multiple chests located within the Order of the Stag stronghold.
You can check this video from KamishTV with all the locations of the chests:
Location of all 13 Brass-Shod Chests
This key opens the forge inside the castle, the one needed for refining the stag shield.
Here:
You can check from distance if the door is open already by someone by looking the door
Open:
Closed:
Sources:
KamishTV Youtube channel
https://tibia.fandom.com/wiki
https://www.tibiawiki.com.br/wiki/
