Hello, Archon!

This happens when you attack the same Warlord with multiple Guardians. When the Guardian, you send first, kills the Warlord, the further Guardians sent to the same target, will return to your City when they reach the target. The Energy is not restored in this case. 

So when does the Warlord reset?....when my Guardian returns to my city?

The guardian will reset once the hit took place.

 If you send a guardian to  Level 1 Warlord

You will have to wait for your Guardian to hit the Level 1 before sending another Guardian to the same Level 1

If you send another Guardian to the same Level 1 -before the first Guardian hit Level 1 Warlord -or is on the way to  same Level 1 Warlord then

you will miss the hit

As already the Warlord is engaged with your first Guardian you sent.

To be able to avoid missing your hits to the Warlord the wise way is to send them to different Level Warlords adequate to the Rank of your

Guardian.

Send different Rank Guardians to different level Warlords and this way you won't miss a hit, or think that The Warlord will engage in a battle on the bases of 1st come 1st served and the others get ignored :) and you will loose the 10 Energy :(




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Adequate Warlord for this Guardian will be Warlord Level 1

What decides this will be the Attack Power Vs Warlords to match the Warlord HP 

So :
Warlord Level 1 HP: 525/525
Guardian Rank 1 Attack Power Vs Warlords 525


There are ways to upgrade your Guardian faster and this possibility should be explored also.

I hope this helps , Good luck!