From what I can see from the game:
Force Pike Basic - Stun Chance upped to 100%, otherwise the same
Imperial Phalanx Special reworked - All DS allies gain Defense Up and Heal over Time for 2 turns and Empire allies gain Health Up and Retribution for 2 turns. Royal Guard gains Taunt for 1 turn.
Unyielding Defender - At the start of the encounter, if the allied leader is Empire, Royal Guard gains Max Health equal to 5% of the allied leader’s Max Health and then doubles his Health until the end of the encounter. (This is the Zeta part.)
At the end of the turn, if another ally took damage that turn, all Empire allies recover 6% Health. Royal Guard Taunts for 1 turn whenever another ally falls below 50% Health.