Kashtira Ashtra

A small Ashtra engine helps you make rank 7 xyzs and level 8 synchros.

Mikumari the Sealing Deity Ashtra searches for Yoa the Plague Deity Ashtra.

Yoa searches for Ashtrashen - Gateway to the Worlds Beyond or Ashtra Cursed Roar.

Mikumari and Yoa can special summon themselves from your hand by revealing and returning a set card you control. They're both level 7 monsters, so you can make a rank 7 xyz by using them as material.

Ashtrashen can send a face-down card you control to the graveyard to search for every other Ashtra card in your deck.

Cursed Roar can special summon itself as a level 1 tuner, then it allows you to synchro summon. You can use this effect to synchro summon on your opponent's turn. Alternatively, you can activate its destruction effect if you control an Ashtra monster or have 1 in your graveyard.

One of the best level 8 synchros you can summon is Adamancipator Risen - Dragite, which can negate your opponent's spell/trap or effect if you have a water monster in your graveyard. Kashtira Ogre and Mikumari will satisfy this activation condition.