First, the Tower of Challenge is extremely solid, even a full-strength attack from a True King Realm can't leave the slightest mark on it.
However, Duo Lai's devouring of Supreme Power can cause some damage to the Land of Challenge.
Yet, the tower itself possesses a very strong self-healing ability, and it doesn't require any materials for self-repair.
Second, the Tower of Challenge contains a vast space, which is also a standard feature of most high-order buildings.
Third,
"Inside the Tower of Challenge, the flow of time is also somewhat different."
"The biggest difference in time flow is within the Challenge Realm!"
It makes sense when you think about it.
For low-level battles, it's fine, but for battles at the Law Realm or even Saint Realm, where the gap isn't too large, it's not impossible for both sides to fight until the world crumbles, lasting days, nights, months, or even years.
