Once this card is out, keep it in defense. By doing this, you have an ultimate defense and you can keep putting EARTH monsters face-down. Then, Flip Summon them to inflict 1000 points of damage to your opponent's life points.
You can bring this card out quickly by suiciding a "Giant Rat" into one of your opponent's monsters to activate the effect of "Giant Rat" to Special Summon "Criosphinx". Then, Special Summon "Exxod, Master of The Guard" by tributing "Criosphinx".
Having "Hieracosphinx" on the field will stop your opponent(s) from attacking your face-down monsters, forcing them to either attack your 4000 DEF "Exxod" or your 2400 ATK "Hieracosphinx". Having a "Guardian Sphinx" face-down will allow you to put all of your opponent's monsters to his/her hand, leaving your opponent open to attacks from you flipping monsters as well as "Hieracosphinx".
Use "Shield & Sword" or "Ojama Country" (Although the latter requires a face-up Ojama monster, many players say it's the best option as it's a field spell that lasts for the entirety of the duel if your opponent has no spell wipe cards) to get a 4000 ATK monster.
Add in DNA Surgery to make it a Machine Type, then Limiter Removal to give it 8000 ATK for a potential OTK.
Use "Battle Mania" to force your opponent to attack this card while "Continuous Destruction Punch" is on the field, inflicting large amounts of damage to your opponent and destroying most, if not all, of your opponent's monsters.
You can deal even more massive damage using "Canyon".
This card can work well with "Great Spirit" (which can be pulled out with "Giant Rat") to switch "Exxod's" ATK to 4000 (make sure you have a back-up card so you don't take a lot of damage and lose an ace card).
Leave this card in attack mode and when the opponent attacks use Desert Sunlight to switch Exxod into defense mode.
Use Shield & Sword to get a 4000 ATK Monster. Then use DNA Surgery to make it a Machine Type. Finally, use Limiter Removal to make it 8000ATK! A powerful OTK!
This card also works well with "Thousand-Eyes Restrict" in tandem with "Tsukuyomi", in order to protect your face-downs from being attacked, as this strategy relies on flipping, not attacking.
You can use "Monster Gate" to get a "Sphinx" card out of your deck (though it requires some luck), summon it on to the field, then you can can tribute it for "Exxod, Master of The Guard", then, use "Monster Reborn" to get back your Sphinx.
You can either summon another after all of this (because they were all Special Summoned), or you can play one at the beginning, to use "Monster Gate".