This variant uses the Speedroid cards to augment a light Kashtira build. It's currently the most viable variant of the deck, with the Speedroids providing versatile endboards to complement the sheer power of the Kashtira, and since it can generate immense pressure off of few cards you're free to run more generics. However, it plays much differently from the other variants.
This variant got a Top 32 showing at the 2023 Germany National Championship, piloted by Aerosol: https://ygoprodeck.com/deck/kashtira-speedroid-332093
as well as a regional top from Paradox: https://imgur.com/a/QCTFKpK
General gameplan: Use the Kashtira cards to generate advantage and then make Dracossack to get RBS access, which then opens up your Synchro plays. Make sure to manage your locks carefully.
Example combos:
Fenrir = Baronne + Piper for 3.5
Unicorn + Fenrir = 50/50 Baronne + Dragster + Fenrir + Piper for 3 / Hrasevelgr + S:P + Fenrir + Piper for 2
Winter_Killz also has a number of videos on the deck, ranging from combo tutorials to test hands, and is another good resource for learning.
Level 7 EARTH Psychic/Effect 2400/2400
If you control no monsters, you can Special Summon this card (from your hand). You can only use each of the following effects of "Kashtira Fenrir" once per turn. During your Main Phase: You can add 1 "Kashtira" monster from your Deck to your hand. When this card declares an attack, or if your opponent activates a monster effect (except during the Damage Step): You can target 1 face-up card your opponent controls; banish it, face-down.
Good generic and searches the other monsters.
Run 3
Level 4 FIRE Warrior/Effect 1500/2100
If you control a "Kashtira" monster: You can Special Summon this card from your hand, also you cannot Special Summon monsters from the Extra Deck for the rest of this turn, except Xyz Monsters. During your Main Phase, if this card was Normal or Special Summoned this turn: You can banish 1 "Kashtira" card from your Deck, except "Kashtira Riseheart"; banish the top 3 cards of your opponent's Deck face-down, and if you banish any, this card's Level becomes 7. You can only use each effect of "Kashtira Riseheart" once per turn.
A tech that makes Fenrir a 1-card combo, since you can search and NS it to make Dracossack unlike Scareclaw.
Run 0-1
Level 7 WIND Psychic/Effect 2500/2100
If you control no monsters, you can Special Summon this card (from your hand). You can only use each of the following effects of "Kashtira Unicorn" once per turn. During your Main Phase: You can add 1 "Kashtira" Spell from your Deck to your hand. When this card declares an attack, or if your opponent activates a monster effect (except during the Damage Step): You can look at your opponent's Extra Deck, and if you do, banish 1 monster from it, face-down.
The main starter; grabs Birth for extension. Has a friendly Attribute and can fuck up a lot of decks.
Run 3
Level 7 EARTH Psychic/Effect 0/2600
During the Main Phase (Quick Effect): You can Special Summon this card from your hand, and if you do, banish 1 "Kashtira" or "Scareclaw" card from your hand or GY. You can only use this effect of "Scareclaw Kashtira" once per turn. This card can attack while in face-up Defense Position. If it does, apply its DEF for damage calculation. If your "Kashtira" or "Scareclaw" monster battles an opponent's monster, that opponent's monster's effects are negated until the end of this turn.
Is an actual extender compared to Riseheart, but requires having access to other Kash cards. Can also help to get rid of threats due to its battle effect.
Run 0-1
Continuous Spell
You can Normal Summon Level 7 monsters without Tributing. During your Main Phase: You can Special Summon 1 of your non-Xyz "Kashtira" monsters that is banished or in your GY. If your opponent activates a Spell Card or effect, and you control a "Kashtira" monster: You can target 3 cards in your opponent's GY; banish them, face-down. You can only use each effect of "Kashtira Birth" once per turn.
Less of a brick when you're running more Kashtira monsters. Good extension and a solid endboard piece.
Run 1-2
Field Spell
When this card is activated: You can add 1 "Kashtira" monster from your Deck to your hand. Monsters you control gain 100 ATK/DEF for each different Attribute on the field. If a "Kashtira Shangri-Ira" you control activates an effect (except during the Damage Step): You can target 1 card on the field; destroy it. You can only use this effect of "Pressured Planet Wraitsoth" once per turn. You can only activate 1 "Pressured Planet Wraitsoth" per turn.
The Field Spell that searches the monsters. Self-explanatory.
Run 3