Each time long distance travel is being used via spells or portals there should be a cost based on the overall strength and the number traveling to prevent RUSHERS from dominating the game with capital blitzes.
Example: If player_A starts near player_B then by rushing player_B kills and acquires his territory and resources I would prefer time to build my empire(player_C) and defend myself instead of some spell or structure providing a method of rushing me as well.
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OTHER THOUGHTS:
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Different types of long distance traveling should also be available such as:
1) Caverns through the Underworld (One Way or Two Way Travel)
A) Traveling to target location is unpredictable, but usually 50% faster. Percentage chance of being attacked by independent beings and things from the Underworld while traveling. The type of attack and number of enemies is completely unpredictable. Any number of units/champions can travel across.
2) Cloud Sailing (One Way Travel)
A) Traveling to target location is 70% faster. Able to view terrain and structures while traveling yet no option to stop or exit along the way. This type of travel sails above the clouds and thus immune to weather events. Strong flying creatures such as wyverns, dragons and air elementals are able to attack the traveling party via flight. Cloud sailing can transport any amount of units/champions yet the larger the size the greater the cost.
3) Flying Ships (Two Way Travel)
A) Traveling to target location is 40% faster. Able to view terrain, armies, and structures while traveling and ability to stop or exit along the way however requires more materials and magic to build. The flying ship travels far below the clouds and thus vunerable to weather conditions and some siege weapons. Any type of flying creatures can attack the crew on the flying ship while it's moving. The flying ship can be used endlessly once created yet has an upkeep to remain flying. Depending on the ship depends on the number of units and type of units.
4) Magic Carpets (Two Way Travel)
A) Traveling to target location is 50% faster. Able to view terrain, armies, and structures while traveling and ability to stop or exit along the way however requires magic to build. This type of travel sails above the clouds and thus immune to weather events. Strong flying creatures such as wyverns, dragons and air elementals are able to attack the traveling party via flight. The magic carpet can be used endlessly once created and has no upkeep. Only a few human sized units may travel for each magic carpet.
5) StarGates: (Two Way Travel)
A) Traveling to target location is instant, however this is a structure which can only be used during a full moon. The structure can work at anytime yet requires activation from a powerful magic item or a powerful magic spell. Any number of units/champions can travel across.
6) Currents in the Oceans: (Two Way Travel)
A) Traveling to target location is 30% faster. Unable to view any terrain, armies, ships or structures while traveling the currents at the bottom of the ocean thus also immune to current weather. Small percentage chance of being attacked by independent sea creatures or sea creatures from an enemy player. Units/Champions will each need some type of temporary or permanent water breathing magic or ability to use this type of transportation. Any number of units/champions can travel across.
7) Teleportation: (One Way or Two Way Travel)
A) Traveling to target location is instant yet target location cannot be unexplored on the map. Any number of units/champions can travel, but it will cost more magic depending on the number of units and their size.