Izoni, Center of the Web has great synergy with our deck since on ETB or attack trigger, we may collect evidence 4 to create two 2/1 black and green Spider creature tokens with Menace and Reach. In addition by sacrificing four tokens we Surveil 2, then draw two cards and gain 2 life. Although that sacrifice cost is high, she does not specify creature tokens, so she has Food token synergy and combined with the Spider token synergy that make her a repeatable and consistent card draw source for our Spider Tribal.
Stinging Study works great with high mana value commanders and is probably a better card draw option, but Izoni, Center of the Web has greater synergy with our deck as she synergizes with many of our strategies being a card draw source, a Spider tokens producer and a sacrifice outlet for Food tokens.
Bedrock Tortoise gives Hexproof to all our creatures on our turn, which is great for protection. It is also a Toughness Combat Damage enabler which has great synergy with our Spider Tribal build since many of our spiders have high toughness. Essentially a 4 mana 6/6 that forces our opponents to play removal at sorcery speed. It is a strictly better card than Ancient Lumberknot for our deck.
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