You can switch from your 40 max energy set to your 25 max energy set

MONKING - Decisions & skills in perspective: Energy hiding: When playing monk, you'll be faced with this boi gold sooner or later: energy denial. They'll try to drain your energy pool dry, making you unable to cast anything. Because of this, it's vital to understand the principles of energy hiding.

The monk comes with a basis of 30 energy, and with a normal staff that will be 40 energy. If you also have a weapon set with a -5 energy sword or axe, you can switch from your 40 max energy set to your 25 max energy set.

The 15 energy differences between these sets are then hidden safely, as energy you don't currently have can't be hit with Energy Burn or the like.

You can switch to your staff, cast a spell or two, and then switch back to your -5 energy set again so that your energy can regain itself without fear of being burned away by the enemy team.

This also works very well with hexes such as Malaise and Wither, since they end the moment your energy reaches zero. With focus swapping to your -5 energy sword, it's not too hard to artificially set your energy pool at 0 energy for a moment.