I'd wager that having Ultimecia, Temporal ThreatUltimecia, Temporal Threat, Displacer KittenDisplacer Kitten, and Verity CircleVerity Circle on your board simultaneously will allow you to run away with any game easily
Many MtG mutate cards have abilities that trigger when they (or another card) mutates
Kuro, Pitlord Listen, not all demons can be winners
Riolu can be obtained from Shining Revelry pack in the Shining Revelry set
Apart from Cosmo Neos, you can also activate the effect of Cross Keeper to banish it and draw two cards
The main win conditions of the deck are winning through combat, burn damage, or by using Approach of the Second Sun