If Sky Splitter is played for 0 might, and an opponent reacts to reduce the player's might (which would make the cost 3 that they can't pay), does Sky Splitter get negated?

Ruling: No, Sky Splitter does not get negated. Once a card is on the chain, you never go back to paying the cost - the cost is paid once at the beginning during the process of playing the card, before opponents can respond.

Sequence:

• The card is removed from its zone and put onto the chain
• The cost is calculated and paid
• The process of playing the card completes
• Only after the active player passes priority can opponents play reactions

Nuances:

• The card enters the chain before the cost is calculated, but this does not give opponents priority - the entire process of playing a card (including cost payment) must complete before opponents can respond
• The active player retains priority after playing a card and may play further reactions before passing
• Opponents cannot get priority before the cost has been paid