Name: Charm Titan
Circles: Earth / Mentalism
Description: The chances target Titan joins your side increase 50%.

Is this a charm spell or a unit enchantment spell?

I vaguely recall Aaron saying you might be able to get a Titan to join you. So as the unit enchantment in the OP I do like this spell. As a one-off charm spell I would think the chance would be fairly low.

The name for the enchantment spell should be along the lines of Calm Titan or Entice Titan.