- Use Submerge to make Cthulhu and any/all units in the same area immune to your enemies' foul intentions until they re-emerge.
- If you re-emerge in an ocean area, you can Submerge once again the very next turn.
- A submerged Cthulhu creates uncertainty in your opponents' plans. The prospect of Cthulhu appearing in any area on the board can affect your enemies' decisions.
- Once Cthulhu has all 6 of his spellbooks, battle becomes unlimited. Use this opportunity to re-emerge on your enemy and battle on the same turn. This can be devastating to your opponents.