In XY's TCG, where the phrase "Mega Evolution Pokemon" last appeared in the TCG, it was defined as "Mega Evolution Pokemon-EX", which is a different name type and evolution mechanic than that of today"s mega evolution cards that skip the "normal" final stage, and are treated as a mega form version of the stage 2, vs
[13] The games introduce Raikou, Entei, and Suicune, some new types of legendary Pokmon that wander around Johto, changing locations frequently in a process known as Roaming Pokmon
Majority "Tenyi" Effect Monsters are under 1500 ATK, qualifying them to give more attacks via "Berserker Soul" at a critical moment
That card will be Mega Signal
Many players had always liked Merfolk and were unhappy with their absence
This way, when the Thopter does come into play, your Foundry is already untapped and so you can sacrifice it to make a Construct without having to worry about a Lightning Bolt in response