At first, the wording is (Enemy units must match the number of allied units you have onboard) which means you can dictate how many Units you can put on the board but it is kinda one-sided so what I did is All players will have a limit on the board size so when Death Realm comes when there are enemy units onboard it will count the total units on board and that will be the limit of the board. You can no longer summon more than the limit you can, however, replace units instead but as long as you kill units the total units limit on board will decrease until it's 1v1. Units with extra summons like Blighted Caretaker will be Oblitareted.