With the release of patch 6.5, you can increase your Island Sanctuary rank from 16 to 20. This page explains each step.
How to Reach Rank 16
If you aren't already Rank 16, please read the Island Sanctuary Rank 12 to 16 guide for a guide to reach rank 16.
Starting with Patch 6.5, at Rank 16 you can purchase a Vicarious Vacationer minion and Colorful Carrotsol fashion accessory from the Horrendous Hoarder under the Exclusive Wares category.
A Subterranean Investigation
The Felicitous Furball in your Hideaway will have a quest for you. (If not, make sure to upgrade all of your buildings and check on all of the logboards to fully complete them.)
Go into the cave in the southern face of the large mountain in the center of the island. Go into the west tunnel and talk to the Determined Digger. Afterward, go to the west edge of the circle on the map and check on the sparkling Point of Interest. Then talk to the Determined Digger once more.
You can now craft the Splendiferous Mammet-sized Spelunking Tools. The required materials are:
- 10 Island Palm Log
- 10 Island Resin
- 10 Island Wood Opal
- 10 Island Marble
- 10 Island Mythril Ore
After you craft it, talk to the Determined Digger in the cave. There will be a cutscene.
After you have explored the new cave and gathered the new materials from it (Island Hawk's Eye Sand and Island Yellow Copper Ore) use the Isle Return duty action to return to your Hideaway. Talk to the Felicitous Furball in your Hideaway to continue.
After this, you need to level up to Rank 17 to proceed.
New Crafting Recipes
At Rank 17, you learn the crafting recipe for the Islekeep's Chisel and Islekeep's Mythril Pickaxe. You will need to make the Pickaxe first, because the Chisel requires materials that can only be gathered after you craft the Pickaxe. The Pickaxe requires the following materials:
- 3 Island Iron Ore
- 3 Island Resin
- 4 Island Mythril Ore
- 3 Island Hawk's Eye Sand
The Chisel, which you can only make after you have made the Islekeep's Mythril Pickaxe (see above), requires the following materials:
- 3 Island Coral
- 3 Island Durium Sand (From Rough Black Rock at Sunrise Lookout (southern face of big mountain))
- 4 Island Gold Ore (From Yellowish Rock in the Mother Lode cave)
- 3 Island Hawk's Eye Sand
With the Island Chisel, you can get new materials from crystal clusters, which can be found the Mother Lode Cave.
At Rank 17, you can renovate your cabin. You will need to craft the Islekeep's Chisel to gather the necessary materials (see above). The required materials are:
- 15 Island Crystal Formation
- 15 Island Yellow Copper Ore
- 15 Island Mythril Ore
- 15 Island Clay
- 15 Island Leucogranite
At Rank 18, you can renovate your Granaries. To renovate both, the required materials are as follows:
- 30 Island Crystal Formations
- 30 Island Yellow Copper Ore
- 20 Island Leucogranite
- 20 Island Clay
- 10 Island Spruce Log
At Rank 18, you can buy new seeds from the Produce Producer:
- Island Watermelon Seeds
- Island Sweet Popoto Sets
- Island Broccoli Seeds
- Island Buffalo Bean Seeds
At Rank 19, you can renovate your workshops and construct new landmarks.
To renovate all four workshops at rank 19, you will need the following materials:
- 60 Island Crystal Formations
- 60 Island Yellow Copper Ore
- 40 Island Mythril Ore
- 40 Island Clay
- 20 Raw Island Garnet
At Rank 19, the following new landmarks become available:
- Sanctuary Sanctuary
- Aetherial Arbor (requires all facilities renovated to maximum and their logboards checked)
Complete "An Idyllic Island"
At Rank 19, after you have renovated all facilities to the maximum and checked their logboards, the Felicitous Furball in your Cozy Cabin will have an exclamation mark. Talk to the Furball to complete the "An Idyllic Island" vision. Afterward, new quests will be available.
After you complete the "An Idyllic Island" vision (see above), talk to the Felicitous Furball to unlock Felicitous Favors. These are special requests from the Felicitous Furball to complete certain workshop handicrafts in exchange for Felicitous Tokens, which you can exchange for rare rewards. You get more tokens for efficiency bonuses, so be sure to schedule the requested items after something in the same category to get the bonus.
The Sweetest Thing
After you complete the "An Idyllic Island" vision (see above), you can also talk to the Curious Courier to start a new quest, "The Sweetest Thing".
At Rank 20, you learn the recipes for Flawless restraints. These require a large number of Granary-exclusive materials, but they are guaranteed to catch Island animals (much like a Master Ball in Pokémon).