So! Its a larger, more expensive Stonegaze Basilisk. I love the flavor! Competitively... I'm underwhelmed.
15 mana, and not an animal (so no discount for Beastmaster) makes this a pretty hefty investment.
THE GOOD
5+ instead of 7+ on the Stuck/Cripple is a major improvement. Stuck is also not a poison condition, so the Spider can hit poison immune creatures (all the nonliving + Malacoda), which Cripple can't. Spider also has a little more health, isn't slow, and as a finishing touch, has Psychic Immunity.
THE BAD
-1 range compared to the Basilisk. Range is synergistic with Restrained effects, so this is an important downgrade.
THE FUNKY
It's not immediately clear to me which has the stronger melee attack. On the one hand, the 4 die bite on the Basilisk is quite adequate for a ranged creature. On the other hand, the Spider's bite is weaker at 2 dice, but has a 1/3 chance of doing 3 points of Tainted. That chance rises to 2/3 if the creature is webbed, which looks kind of like a tie: 4 = (2/3)*3 + 2. But tainted is harder to heal than damage, and (more importantly) it ignores armor. So I give a slight edge to the Spider if the target is restrained, and the edge to the Basilisk otherwise.
I should also point out that Slow doesn't seem to be much of a hindrance to the Basilisk because--like all (?) creature ranged attacks--it takes a full action to attack anyway, so it can't move and attack no matter what, and it doesn't need to move much in the first place.
Over all, Basilisk seems better to me because of its longer range and lower cost, but I can see a Beastmaster saving spellbook points by chosing the Spider if the major purpose of the creature is to ground flyers, not stop a rush. Still, its not an animal, so no ring and no lair, so the Beastmaster doesn't lose much at all by "downgrading" to Basilisk.
I feel like 5+ is quite good, but it's not an amazing 4+ with a bonus at 10+ like Gorgon archer has, so even though it's more reliable, its not so reliable that its a solid answer to a specific and immediate threat (e.g. turn 3 assault by Lord Of Fire). It's more generally a good answer to a flyer heavy swarm strategy where there will be many opportunities to make the Stuck roll.
Which makes me wonder if the Spider will just be outclassed by Gravicore.
I'm not disappointed, just wondering what I'm missing.