Once per turn: You can send 1 "Elementsaber" monster from your hand to the GY, then target 1 "Elementsaber" or "Elemental Lord" monster in your GY, except "Elementsaber Nalu"; add it to your hand. Once per turn, if this card is in the GY: You can declare 1 Attribute; this card in the GY becomes that Attribute until the end of this turn.
Elementsaber Malo and Palace of the Elemental Lords can pitch Elementsaber and Elemental Lord monsters to the graveyard to be recovered by Elementsaber Nalu.
Elemental Lord monsters can only be summoned when a specific number of monsters in the graveyard share a certain attribute. This makes Elementsabers perfect for summoning Elemental Lords because they are able to adjust their attribute while in the graveyard.
Invocation uses cards from your graveyard as materials and depending on the attribute of the monster paired with Aleister, summons an Invoked monster. Elemental Lords can change their attribute in the graveyard to let you Fusion Summon the Invoked monster you need.