Sephiroth, Fallen Hero

The "modified creature" theme usually means Auras and Equipment stacked onto small aggressive bodies, but here the whole subtheme gets weaponized into a curve-topping threat and a recursion engine at once. The attack trigger is the clever part: dropping a cell counter onto a target makes that creature "modified" and slams every modified creature you control up to base 7/5 until end of turn, which is both a mass pump and a way to launder your own board into the modified category so The Reunion has fuel. That second ability is what gives the card teeth past a single combat. Sacrifice any modified creature (including one you just marked with a cell counter) and it walks back out of the graveyard, so it wants a board built to feed itself: cheap Equipment carriers, Aura targets, token generators wearing a single counter. The tension the design resolves is that a five-mana 7/5 with no evasion and a fragile toughness would normally trade down and die, but Jenova Cells turns every attack into a threat-inflating engine and The Reunion makes killing it a temporary measure at best. It rewards a build that treats modification as a resource to be spent and rebought rather than a permanent enchantment stack, which is a genuinely different way to attack the Voltron-adjacent space most modified-matters cards live in.