So this ones mediocre, but still its got 5 health. The average turn 5 play doesn't have 5 attack. So, were going to be seeing a ping + card or a card + card going into this for removal or even straight up spot nuke which is amazing for your late game.
This is a good arena card. Really this card is like 5 mana (infinite) attack/5 health when dealing with other minions as long as it isn't silenced. This will trade into anything with 4 or less attack (the usual turn 4 minion plays), kill it (as long as the minion doesn't have divine shield) and live, where the opponent will need to ping it somehow and waste mana on turn 6. While it doesn't have taunt its a minion that the opponent needs to deal with by either trading their worst minions or using removal.
People undervalue poison effect in constructed, but arena this will see some play. Just like you barely see Stubborn Gastropod or Giant Wasp in constructed, but they both aren't bad cards to pick in arena especially if you are lacking removal even though both are easily susceptible to 2 damage board clears.
However, in Arena, this card is a solid pick because on turn 5 it's basically a 6/5 and will trade into your opponent's 5 drop and, on top of that, if your opponent is struggling to maintain tempo you can get a double trade with this minion to counter two of your opponent's turns. Also, since it has 5 health, it will be difficult to remove with could lure out some large removal. This is especially good for Priest because 1) they can continue to heal it or give it Health to take out multiple low attack targets like Stegodons and 2) they have the best counters available against this (PoM, SW:P, etc.).
Overall, a good arena card. Very similar to Maexxna but will appear a lot more often in Arena due to the rarity and appearance bonus.