This is against Nynomax using a water tank and two air cannons. With upgraded gear and max rank, decimates can destroy him pretty easily. The key is to use your water pet's 5th ability and the air pet's 5th ability on the first turn. Use your standard first ability attack the second turn. Use Water's Tidal surge on turn 3 and air's Torrential blow on turn 3. Continue to build mana using your first ability until you have enough mana to decimate. When decimate is ready, use it and the battle should be over~ :)

Twas a while ago. :p

"Turn 98: Xerxes's Decimate Critically Hits Crystalline Behemoth for 649,775 Physical Damage!"

I have a video on what I did:
The Battle
I added a laugh track to it because that was almost how I laughed after that last hit. X'D

I still can't finish the South side yet. I'm still ranking my second air kid to 5. He's rank 4 in everything so we're almost there. XD

I also need to upgrade the red gear and get some more red gear for my other air kid and Sunstar. :'3

Same battle tactics as the first time. Nyno was at 52k when Decimate went off. I almost didn't get to use it. TwT

Turn 21: Voulges Force's Decimate Critically Hits Ancient Temple Guardian for 507,311 Physical Damage!

horrible horrible beast, throw Ancient Temple Guardian in the trash