Summon "Labradorite Dragon", then use the effect of "Level Eater" to Special Summon itself from the Graveyard (lowering "Labradorite" by 1) to easily Synchro Summon this card.
Because "Underground Arachnid" equips your opponent's Monster Cards to this card, you can use "Release Restraint Wave" to not only get rid of the equipped opposing monster, thus making it able to use its effect again, but to also destroy all your opponent's face-down Spell and Trap Cards.
"The Dark Door" will make this card invincible in battle (except by monsters that can attack multiple times like "Tyrant Dragon").
Special Summon "Infernity Avenger" when a Level 6 monster gets destroyed, then use "Level Eater" to reduce the Level of "Avenger" to summon "Underground Arachnid".
Use cards like "Lava Golem" and "Grinder Golem" to get monsters out onto your opponent's field quick, and then use cards like "Enemy Controller" to change the battle position of the opposing monsters. Either way, you can get a monster out onto your opponent's field to equip to, perhaps as a defense for when "Underground Arachnid" might be destroyed, and, depending on which "Golem" monster you used, you could have inflicted damage 1000 damage to your opponent, or have gotten a "Grinder Token".
This card works well with the "Scrubbed Raid" Trap card, since you can send the monster you have equipped to "Underground Arachnid", and end the battle-phase (While taking no damage from a higher ATK Monster). On your next turn, use the effect of "Underground Arachnids" to equip the attacked monster.
Although the one-piece "Meklord Emperor"s absorb Synchro Monsters, this card (if Summoned after a Meklord Emperor) can equip the "Meklord Emperor" as an equip card (thus this card won't be absorbed).
Use equip cards to increase the low ATK of this card; "Mage Power would be a good choice.