Rhasa the Sunderer

*Q. I have 10 cards in my Trash, including a <Rhasa the Sunderer>, and a <Last Rites> equipped to a unit. When the unit hold, can I play Rhasa the Sundere for only 1 Chaos Power?

No. As you target Rhasa with your Last Rites, Rhasa is removed from your trash and put onto the Chain.

351. Playing Cards
STEP1: Remove the card from the zone you are playing it from and put it onto the Chain. STEP3: Apply discounts in any order.

At the time you apply the discounts, Rhasa is no longer in your Trash therefore the discount is only 9 Energy.