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.