Gift of Reason is a Level 5 Thaumaturgy that requires 4 and consumes 20 on use. It elevates a unit who isn't Mindless to the rank of Commander, giving them a number of added functions:

• It lets you give them commands on the strategic map.
• It lets you Script their first five actions in battle.
• It lets you equip them with Items.
• It activates their Magic paths and their Leadership scores, giving them impact. (For example, Indirect Magic begins to work.)

Contrary to the Ritual's description, it does not actually make the unit smarter. It simply lets you play with them directly.

Divine Name is a Level 7 Thaumaturgy that requires 5 and consumes 25 on use. Aside from the requirements, Divine Name's only difference from Gift of Reason is that it also works on the Mindless. Contrary to the name, it does not make the unit Sacred.

Divine Name is far-less redundant than it seems, since the Astral path provides you with a couple of effects that can give you units you'd much rather have as Commanders; Enslave Mind and Wish, to be specific. The former also happens to be a Thaumaturgy. On the other hand, Nature's equivalent to the former can give you Commanders. If you can cast both, you should cast Gift of Reason, simply because it's cheaper.

No, unless you're memeing. Gems aren't cheap. That being said, it does cut costs in a couple areas:

• Unless you need to use Alchemy for the correct Gem type, using this is always cheaper for getting a Magic path you don't have than Empowering, provided that you don't screw up and use this on the wrong guy. It's notably one of the only ways to convert Gems into levels in Blood, and far more consistent than betting on an Ether Lord or a Lamia Queen having what you want.
• A few nations have late-game Summoning "bundles", which give you a powerful Commander along with a good handful of units that can also be powerful Commanders; you might as well use Divine Name (or Gift of Reason) on those units, instead of summoning them individually as Commanders. It's always cheaper.

Several units can only be summoned as units, but have hidden magic paths that are activated upon having Divine Name or Gift of Reason cast on them. These include:

• EA Lanka, MA Bandar Log, and LA Patala's Asrapa 11 and Danava 2250%
  50%
  50%
  50%
• The Mediterranean nations' Ker 11 and Lampad 121
• MA Na'ba's Jinn Warrior 22
• MA R'lyeh's and LA R'lyeh's Vastness (from the Void Gate) 3
• Marignon and MA Pythium's Angel of the Heavenly Choir (from Heavenly Choir) 2
• Most Tartarians (though Tartarian Gate sometimes gives Commanders)
• Gnomes 22 (though these are typically recruited as Commanders)
• Juggernauts (from Juggernaut Construction) 3