when mercenary pass End The Mark wil rest
What is this new "Mark" thing ?
U can buy weapons from mercenary pass shop with it
No, " Marks will be carried over to each season if you don't redeem them all and you can save them for the next season "
Read the FAQ section from mercenary pass webpage (bottom left - click on Mercenary Pass Shop ) :
No, it'll stay to the next season
How can I get mark?
Complete mercenary pass to level 70 and you'll receive 10 marks for free pass and 20 for premium pass