Can you use Kai'sa Legend's mana gain ability to prevent an opponent from using reactions, or does it fall off the chain and pass priority?

Ruling: Mana gain abilities cannot be reacted to, but they do not prevent opponents from using reactions afterward. There is no "chain blocking" - the chain only resolves when both players pass priority without adding anything.

Sequence:

• After you use a reaction, your opponent gets priority to use reactions
• While you have priority, you may use multiple reactions before your opponent gets priority
• The chain resolves only when both players pass without adding anything

Nuances:

• The "cannot be reacted to" text on mana gain abilities means opponents cannot react to you adding energy to play a unit, not that it blocks further reactions