Halloween Boss Portals - Smart Strategy or Exploit?

[Cinco]

Please take a look at this video (only for reference, not pointing at anyone) (link to video) here. It doesn't seem to cost the player an extra energy to join Oligarch's mansion after completing in Boogie's mansion.

This is true - it only costs energy to enter the Spooky Woods. It costs candy bags to enter Oligarch and Boogie.

It's not meant to cost you additional energy to go through the event portals inside Spooky Woods.