Combine two columns of alphanumeric data into one, with no duplicates, in descending order

Hello,

I hope this is a simple question, though I haven't been able to find the answer by searching online. I'd like to find a formula/array which will allow me to consolidate alphanumeric data from two separate columns into one, without listing any duplicates, in descending order.

Please see attached example. The columns to be consolidated are A and C (Past Years and Currently Active); column E (Consolidated) is how the end result should look.

Can you help me?

~ Melanie