"Lemuria" may also be used in a "Nimble" Deck that focuses on the WATER "Nimble" monsters ("Angler", "Sunfish" and "Manta") as you can Summon 3 of them with little effort. Activate "Lemuria" and all 3 Level 2 monsters will become Level 5, then you can overlay two of those for "Crystal Zero".
This card can evade cards like "Bottomless Trap Hole" by targeting itself for its own effect when Summoned (in the same manner as the "Shrink" Quick-Play Spell.) This tactic can also be applied to any other monster you Summon afterwards.
Note that unlike "Number 73: Abyss Splash", this monster's effects can be used multiple times per turn– even on the opponent's turn or on the same monster. Also unlike "Abyss Splash," whose effects end during the opponent's turn, the ATK of "Crystal Zero" changes last until its owner's End Phase– a detail which can be used to debilitate an opponent's monster for extended periods of time if the effect is triggered during the enemy's turn.
You can Xyz Summon this card by first using the effect of "Instant Fusion" to Fusion Summon "Sea Monster of Theseus", and then Tributing it to Tribute Summon "Salvage Warrior". Use the effect of "Salvage Warrior" to Special Summon "Sea Monster of Theseus" from your Graveyard, and then overlay the two monsters to Xyz Summon this card.