What makes it weaker than other epic spells is how specific your deck has to be built in order to actually ensure you can close games out once you cast Undying Flames
Imagine, as an example, that there were two sets of White Knights available for a given build: Your normal White Knight, and then a variant we'll call "Life Knight" that doesn't have protection, but instead gives you three life when it arrives to the battlefield
Its fine to encase a trading card in plastic and get a standardized look at the condition under the watchful eye of an expert, but at that point, you are taking the item off the table as a playable card
Upgrade 7 What's better than having one copy of a thing
For example, if an enchantment creature with the bestow ability (an ability that allows a creature card to be cast as an Aura instead) is an Aura and the target of Kaya's last ability, the ability will not create a copy of it