If I play Cruel Patron, and I have a unit alone at a battlefield I control, I choose to kill my Recruit to pay the additional cost of Cruel Patron. Can I play my Patron to that battlefield?

Yes, you can play Cruel Patron to that battlefield in this scenario.

According to Rules FAQ Clarification 2026-04-29 (updating rule 187.4.c):

• Ruling: You can summon Cruel Patron to the battlefield where your lone Recruit was killed to pay the cost.
• Reasoning: Because Cruel Patron is currently on the chain, you do not lose control of the battlefield when sacrificing your last unit to pay the cost. Therefore, that battlefield remains a valid location for the placement of your Cruel Patron.