Other 6 Cards for TTTT

Unknown Material Machine/Dark/Level 4/Effect/1500/1300
You can Special Summon this monster from your hand by tributing 1 monster you control. If this monster was Special Summoned it is treated as 2 Xyz Materials for an Xyz Summon. (If this card is Detached it is treated as 1 Xyz Material) When this monster is Detached from an Xyz Monster and sent to the graveyard; you can discard 1 card: Special Summon it in face-up Attack Position on your side of the field. This monster cannot declare an attack on the turn you activate this effect. When this card is Detached from an Xyz Monster; if you control 2 or more face-up Xyz Monsters: banish this card instead.

Spi-Ritual
Ritual Spell
Choose 1 Ritual Monster in your hand, shuffle a number of Spirit Monsters from the field or your hand whose total Levels equal that Ritual Monster's, then Ritual Summon 1 of that the Ritual Monster. You can shuffle this card from the Graveyard into the Deck to target 1 Spirit Monster in your Graveyard; return that target to the hand.

Envious Snatcher
DARK
Level 4
ATK/1200
DEF/1000
[Reptile/Effect] When a Reptile-Type monster battles, it gains 700 ATK during damage calculation only. If a Reptile-Type monster you control destroyes a monster by battle and sends it to the Graveyard, you can Tribute this monster to Special Summon the destroyed monster to your side of the field at the end of the Battle Phase.

|Saleom, Guardian of the Sea|0|ICE|Winged-Beast|Water|7||2600|2800|Cannot be Normal Summoned/Set. Must be Special Summoned (from your hand) by having exactly 5 WATER monsters in your Graveyard, and cannot be Special Summoned by other ways. When this card is Summoned: place 4 Storm Counters on it. During your opponents End Phase: Remove 1 counter off this card and inflict 500 damage to your opponent. While this card has 1 or more "Storm" Counters on it, monsters your opponent controls cannot declare an attack.|

|Roaring Waters|0|ICE|Spell Card|Spell||Continuous|||Each turn, the first face-up Aqua, Fish, or Sea Serpent-Type monster you control that would be destroyed by battle, is not destroyed.|

|Crevice Crawler|138|TIR2|Insect/Effect|Dark|3||1200|1350|When this monster is Summoned; target 2 monsters in your Graveyard with the same name: Special Summon those targets face-up on your side of the field, their effects are negated and they cannot be used as Xyz or Synchro Materials. This monster cannot be target for an attack or for the effect of a card while at least 1 of the 2 monsters summoned by this effect remain face-up on your side of the field. While this card remains face-up on your side of the field: cards in the graveyard cannot be targeted, except by their own effects.|

Can you use Unknown Material Machine as the only monster for a Xyz Summon?

If the requirements for the Xyz monster are "2 Level 4 Monsters" then yes.

what is TTTT?

that's the next set TB