I broke the game. How to move at sonic speed

Step 1. Equip a shield that gives +10% movement speed)
Step 2. Buildstacks of Phalanx Defense
Step 3. Let your stacks of Phalanx Defense wear off while you are at full shields
Step 4. Enjoy

Every time you lose a stack of PD at maximum shield you get another +10% movement speed passive that stacks with the original (this is most likely an exploit/not working as intended). Have fun.

Video examples