The Tone Rebellion/Unlocks & Upgrades

Over the course of the game you will want to be able to access more powerful units and units with different abilities. There are two ways to do this.

Bridge unlocks
Opening bridges between islands not only gives you access to new areas of the map; it also unlocks additional building types that you can build, which then allows different units to be built. This can also allow you to upgrade existing buildings to a higher level, which then allows that building to support additional units of a higher level. Since the number of bridges available is dependent on universe size, playing on a smaller map will mean that less unlocks are available in such a game. However, the higher level unlocks may not be necessary.

Upgrading a dojo is very important. A floater cannot gain a level unless it has the required amount of experience AND has a dojo that has space for units of that level.
 * A level 1 dojo can support 3 warriors at level 1
 * A level 2 dojo can support 3 warriors at level 1 and two warriors at level 2
 * A level 3 dojo can support 3 warriors at level 1, two warriors at level 2, and one warrior at level 3.

The exception are spell towers - spell towers support wizard units instead of warriors. Spell towers support a number of wizards equal to their level, and the highest level wizard it can support is equal to its level. A spell tower will never hold more than one wizard of any given level.

Level 1 and 2 dojos can teleport to a medium or large tone node, but a level 3 dojo can only teleport to a large node. Since large nodes are fairly rare it can be worthwhile to hold back and not upgrade all your dojos to level 3 until late in the game (though having one or two at level 3 is not too difficult). You can still upgrade a dojo to level 3 even if it is on a medium node.

Here is a list of upgrades based on number of bridges opened:
 * 0 Bridges opened: Only first dojo type available
 * 1 Bridge opened: Unlocks second dojo type
 * 2 Bridges opened: Unlocks spell towers
 * 3 Bridges opened: May upgrade 1st dojo type to level 2
 * 4 Bridges opened: May upgrade 2nd dojo type to level 2
 * 5 Bridges opened: May upgrade spell towers to level 2
 * 6 Bridges opened: May upgrade 1st dojo type to level 3
 * 7 Bridges opened: none
 * 8 Bridges opened: Unlocks final dojo type 8 is the maximum number of bridges for a small universe
 * 9 Bridges opened: May upgrade 2nd dojo type to level 3
 * 10 Bridges opened: May upgrade spell towers to level 3
 * 11 Bridges opened: none
 * 12 Bridges opened: May upgrade final dojo type to level 2

Artifact upgrades
Throughout the game you will find artifacts, and when these artifacts are delivered to the correct Mystic Locations, a glyph becomes unlocked. You need to unlock all the glyphs to finish the game.

You could wait until the end of the game to unlock these glyphs, since the glyphs allow you to destroy the spires surrounding the Leviathan on the final island of Friid; once all the spires have been destroyed the Leviathan is defeated. If you haven't accessed the island of Friid yet, this ability isn't useful, and most players will destroy all the enemies on Friid first before doing this, which means you can destroy the spires at your leisure.

However, unlocking glyphs also grants additional bonuses. These bonuses can affect the stats of units, features of dojos, or general gameplay. If you open your tribal display there are small square icons that indicate which upgrades have been unlocked (see images on the right). Looking at the dojo display will also show icons that affect the specific units of that dojo.

As with bridges, size of the universe determines how many glyphs are available. The upgrades are not necessarily tied to specific islands and instead are organized in a specific order. As with bridge unlocks the later ones are only available in larger universes.