Relentless Rats gets +1/+1 for each other creature on the battlefield named Relentless Rats
Thawing Glaciers hasnt been playable in any online format other than commander, so it weights in at a paltry 3cT
3 Dark Confidant Emet-Selch, Unsundered Esper Terra Gogo, Master of Mimicry Golbez, Crystal Collector Hope Estheim Joshua, Phoenix's Dominant Kefka, Court Mage Kefka, Ruler of Ruin Kuja, Genome Sorcerer Mysidian Elder Quistis Trepe Shantotto, Tactician Magician Summon: Esper Ramuh Tellah, Great Sage Terra, Magical Adept The Emperor of Palamecia The Lord Master of Hell Trance Kuja, Fate Defied Venat, Heart of Hydaelyn Vivi Ornitier Xande, Dark Mage
2010-06-15 Training Grounds can reduce the part of an activation cost represented by generic mana symbols down to nothing, as long as it still costs at least one mana
While I have already written an article featuring both Rapid Strike Urshifu VMAX (Battle Styles) and SingleStrike Urshifu VMAX (Battle Styles), there are plenty of great new concepts to explore
So, at this point, you pretty much have to assume anything is possible