The indestructible it grants is very important, as it removes most of your opponents options for getting their commander back in the command zone
Wizards has and may continue to print special versions of cards not meant for regular gameplay, like oversized cards
Red spells often deal direct damage to targets or destroy artifacts and lands, while red creatures are quick and have high power, such as elementals, goblins, and most of all, fearsome dragons
All of these cards can be cast for their front side casting cost, or the alternate More Than Meets The Eye cost, to have it enter the battlefield converted on its back side, similar to transforming effects found on many werewolf cards
Thats pretty much the Djinn in a nutshell
If the creature you control is an illegal target, you won't put two +1/+1 counters on it even if you have delirium