The two Synchros that form Phoenixion have been revealed! (And yes, they Accel Synchro)

Crystron Quondam

Level 4 WATER Machine-Type Synchro Tuner Effect Monster

ATK 1800

DEF 2000

1 Tuner + 1 or more non-Tuner Monsters

(1) During your opponent’s Main Phase or Battle Phase, you can: Immediately after this effect resolves, Synchro Summon using this card you control (this is a Quick Effect).

(2) If this Synchro Summoned card is destroyed by battle or card effect: You can target 1 “Crystron” monster in your Graveyard, except a Synchro Monster; Special Summon it.

Crystron Ametrix

Level 5 WATER Machine-Type Synchro Effect Monster

ATK 2500

DEF 1500

1 Tuner + 1 or more non-Tuner Monsters

(1) If this card is Synchro Summoned: You can change all face-up Special Summoned monsters your opponent controls to Defense Position.

(2) If this Synchro Summoned card is destroyed by battle or card effect: You can target 1 “Crystron” monster in your Graveyard, except a Synchro Monster; Special Summon it.

And for a reminder:

Crystron Phoenixion

Level 9 WATER Machine-Type Synchro Effect Monster

ATK 2800

DEF 2000

1 Tuner Synchro Monster + 1 or more non-Tuner Synchro Monsters

(1) If this card is Synchro Summoned: You can banish all Spell/Trap Cards your opponent controls and in their Graveyard.

(2) If this Synchro Summoned card is destroyed by battle or card effect: You can target 1 other monster in your Graveyard; Special Summon it.

Source