The deck

Why Therions

The reason for playing Therions in Sky Strikers is twofold:
First, because Therion “King” Regulus grants you access to Spell / Trap negation, letting you protect yourself from blowout cards such as Harpie’s Feather Duster, Lightning Storm and Evenly Matched as well as giving you an additional layer of interaction.
Second, because Therion Discolosseum works really well with Sky Strikers by either letting you send 2 Spell cards from the deck to the graveyard with Sky Striker Ace – Hayate (1 from her own effect and 1 from Therion Discolosseum sending another copy of itself from the deck to the graveyard to protect her) or by making it so your opponent needs 4 attacks to remove your Sky Striker Ace link monster if you have a Sky Striker Ace – Raye in the graveyard.
It is also worth mentioning that Therion “King” Regulus sends himself to the graveyard as a cost when activating his effect allowing you to still activate your Sky Striker spells on the same chain if need be.
One more thing to note is that Therion “King” Regulus not only protects your Crystron Halqifibrax and Selene, Queen of the Master Magicians while link climbing into Accesscode Talker, but it also allows you to OTK the opponent even if he is at 8000 Life Points (5300 ATK Accesscode + 2800 ATK Regulus = 8100 damage).

Therions with no Sky Striker Ace monster

It is true that the Therion engine doesn’t really do anything when you don’t open a Sky Strike Ace monster, but realistically you are losing almost all of the games in which you don’t find a Sky Strike Ace monster during the first 2 turns anyway.

Why 3 Roze

As mentioned above, seeing at least 1 Sky Striker Ace monster is crucial, so you would rather take the 5% higher chance of seeing 2 Sky Striker Ace monsters in your opening hand than take the 5% higher chance of seeing 0 Sky Striker Ace monsters in your opening hand.
Also opening Sky Striker Ace – Roze along with Sky Striker Ace – Raye when going second isn’t the worst thing in the world since Sky Striker Ace – Roze can be used to chain block your Sky Striker Ace – Kagari‘s effect to add a Sky Striker Spell back to your hand, allowing you to play around certain negates such as Ghost Belle & Haunted Mansion, Baronne de Fleur, Borreload Savage Dragon, etc.

Eagle Booster

Sky Striker Mecha – Eagle Booster was a last minute inclusion with the idea that it will either let you protect your Crystron Halqifibrax, Selene, Queen of the Master Magicians and Accesscode Talker when going for the kill or buy you an extra turn by making it really difficult for your opponent to OTK you.
Looking back at it, Called by the Grave would have been a much better card to play in that spot.

Closing thoughts

All in all the Therion engine may not be the de facto best way to play Sky Strikers, but it is definitely a breath of fresh air for anyone who has been playing Sky Strikers for some time now.