overly complex plan gooooo
Spend countless frustrating years inventing a Probability Jumper.
Jump to a new universe and watch civilization unfold. Provide nudges in a million places, becoming a figure of legend here, a silent gear in the background there. Develop immortality sometime along the line.
And eventually... eventually... invent a spear.
Tilt civilization just so, causing the perfect wall-breaking spear to be created.
Another eternity; build an army of spear launcher tanks.
Further develop the probability jumper... and warp the whole group back to the wall.
Fire everything.
Probability-jump the jumper itself and the army out of existence once all ammo is spent, and become less immortal to prevent any damage to the timeline.
Then walk up to the wall...
and poke it rather rudely.