The general look of the body does look like some kind of a giant mutant caterpillar or tardigrade, but it's just such a weird-looking creature
The game is probably older than some of you reading this right now
While Arna can easily become an absolute powerhouse, with a wide variety of possible builds available, this Commander has not seen the same amount of fan attention as Nadu or other MH3 favorites like The Necrobloom and Ulalek, Fused Atrocity
Rally the Ancestors can be used in a similar way, but Faiths Reward goes a step further by reanimating noncreature permanents the kind of power which got Second Sunrise banned in Modern for enabling combo decks like Eggs and KCI
Casting Ophidian Eye triggers Yshtolas damage to opponents, but you wont get its card draws by casting it
The willpower icon is how much damage it takes before the character or location is banished