That ability is When the last defense counter is removed from this permanent, exile it, then you may cast it transformed without paying its mana cost. (2023-04-14) As a Siege enters the battlefield, its controller chooses an opponent to be its protector
Half of which came from WAR and ruined different formats in one way or another
Keeping the above because it took me a long time write and I don't want to undo the effort
Steadily over the years my skills have improved, as has my collection, and here we are
While the reprogramming tended to keep most Robobrains from going murderously mad at the realization of what they'd been transformed into, hundreds of years without maintenance has completely circumvented such failsafes, leaving even most non-hostile Robobrains a little bit loopy
This set has a +1/+1 counter theme and a light interplay of artifacts