[EX2-007] Mother D-Reaper is, despite its huge 15000 DP, a Digitama. It is unable to attack, and cannot be affected by your opponent's effects therefore cannot be suspended, returned or deleted conventionally. The only probable way to remove this Digimon would be to attack it while unsuspended, which is no easy feat due to its massive DP.
Meanwhile, [EX2-055] Reaper can be played for free by trashing 7 Searchers from Mother, and will be able to attack multiple times on the turn it is played.
So the engine is actually quite straightforward: grow Mother D-Reaper by putting a ADR-02=Searcher from play or hand to the bottom of its digivolution cards once every turn, and play a Reaper once Mother has 7 digivolution cards.
At a minimum, Reaper would be able to attack 4 times for having 7 Searchers in trash, but it should not be difficult to setup another Searcher in your trash for 5 hits, which is pretty much an endgame play. However, how long do we need to setup Mother's 7 digivolution cards for that to happen?