Master Transmuter does not have summoning sickness.
({U} magic symbol) available.
Steps
Activate Master Transmuter by paying ({U} magic symbol) , tapping it and returning Breya from the battlefield to your hand, putting Breya onto the battlefield from your hand.
Breya enters the battlefield, creating two 1/1 Thopter artifact creature tokens.
Activate Clock of Omens by tapping the Thopters, untapping Master Transmuter.
Activate Phyrexian Altar by sacrificing a Thopter, adding ({U} magic symbol) .
Repeat.
Once you have infinite creature tokens and infinite colored mana, you may activate Breya's ability infinite times.
Results
Infinite colored mana.
Infinite damage.
Infinite death triggers.
Infinite ETB.
Infinite lifegain.
Infinite lifegain triggers.
Infinite LTB.
Infinite sacrifice triggers.
Infinite tapped creature tokens.
Reduce any number of target creatures' toughness to zero.