If you have two Sun Discs and tap both of them, does the next unit enter ready and the second unit also enter ready, or do both effects apply to the same unit redundantly?

Ruling: Both Sun Disc effects apply to the same next unit redundantly. The second effect does not carry over to a subsequent unit.

Sequence:

• Tap both Sun Discs, creating two delayed passive abilities
• When you play the next unit, both delayed passive abilities see it and apply
• Both effects make the unit enter ready (redundantly)
• Both effects are consumed on that one unit

Nuances:

• To have two units enter ready, you must tap one Sun Disc, play a unit, then tap the second Sun Disc, and play another unit
• Sun Disc creates a delayed passive ability (similar to Ravenborn Tome), not a replacement effect or trigger
• The effect specifies "the next" unit, which means each effect only applies to the next unit it sees, not subsequent units
• Even though applying both effects to one unit is redundant, the game has no way to know this in advance