Once considered such a powerful creature that it was given the prestigious nickname 'Superman', the Magic: The Gathering card Morphling hasn't seen much play in recent years - or any years since the late 90s for that matter - but now it's back and rising in price thanks to its role in the increasingly popular Premodern format. While at the beginning of the year you could grab a near mint copy of this card for about $10, now you'd be lucky to find the same for $50.
Released in the ultra powerful Urza's Saga MTG set in 1998, Morphling is a five mana creature with a frankly ludicrous number of abilities. It can fly, make itself untargetable, untap itself, and change its stats, all with the application of a little bit of mana.
Morphling made a name for itself (and gained its superhero moniker) the year after its release. When the dread Combo Winter thawed with a massive spate of bannings in 1999, Morphling rose up from the ashes, an unassuming critter becoming the dominant lifeform after a mass extinction event.
It helped that around this time Wizards embarked on a decade-long experiment with a rules change that put combat damage on the stack. With enough spare mana you could now use Morphling in combat as a five power indestructible creature, buffing it up to a 5/1 to put five damage on the stack, then paying more mana to change it into a 1/5 (or, theoretically, a -4/10) to withstand any amount of damage coming back.
While that rule was reverted in 2009, Morphling is doing the same job in Premodern as it did on the competitive circuit in the 90s, acting as a powerful threat in Control decks. In particular, the top-tier Stiflenought deck often runs a couple of copies.
Control is the natural home for the card, as it's a massive mana sink which is difficult to block or attack into - due to threat of activation. A Control deck can make good use of the mana if you don't need to use it for Morphling, as you can invest it into counterspells and card draw.
Morphling is a Reserved List card with no reprints, so naturally there aren't many copies in circulation. Though there wasn't much demand for the card up to now, it does occasionally get picked up by commander players running Mairsil, the Pretender. Naturally, a big bump in interest was bound to set this card a-spiking.