Can Discipline target Shen when both are played as reactions in the same chain, given that Shen is a unit that can be played as a reaction?

Ruling: Yes, Discipline can target Shen. When Shen is played as a reaction, he immediately exits the chain and enters play as a unit, making him a valid target for Discipline played in the same chain.

Sequence:

• Shen is played as a reaction and goes to the chain
• Shen immediately exits the chain and comes into play as a unit (no player can react to this)
• Discipline can then be played and target Shen

Nuances:

• During a Showdown, if Shen is the only item in the chain, focus passes to the other player after he's played, allowing them to use Actions before Discipline can be cast