Yun Yi was surprised…
Not too many of Noah's experimental subjects had managed to survive, after all, the term 'experiment' naturally carried the meaning of uncertainty and instability.
Po Nan had let Noah implant a mutated branch of the World Tree inside his body, and since Noah inherited Negary's personality, he would definitely not grant others any safe powers that could be used right now.
He only ever granted items or knowledge that required adaptation and modification by the individual to be usable, or the power had flaws that put the user into a dangerous situation; only by surpassing one's limit would they be able to truly obtain that power.
Additionally, since the Celestials already had a natural path of growth, choosing to ask Noah for power was actually a shortcut, so the limit they had to surpass was greater than normal.