If you cast Darius as the second spell in your turn, will his effect trigger and enter ready, or would you have to play another spell after playing Darius for the effect to trigger?

Ruling: Darius would not trigger and enter ready when cast as the second spell, because Darius himself is not a spell.

Nuances:

• While the general rule allows game objects to see themselves entering a zone when their trigger condition is met, this does not apply to Darius because units are not spells in Riftbound.