Thicket Basilisk

The original deathtouch, printed before deathtouch was a keyword and shaped entirely by the combat step rather than the damage step. The petrifying gaze is gated through blocking: the basilisk has to be in combat with its target, and the kill resolves at end of combat rather than on damage. The ability already cuts both ways, firing when the basilisk blocks or becomes blocked, so it threatens attackers and defenders alike; what it cannot do is reach a creature it never meets in combat. Exempting Walls is the tell that this is a creature-type design rather than a damage-based one; walls were the canonical non-attackers of the era, and carving them out keeps the basilisk from being a universal answer to defensive boards. Everything that came later (Cockatrice, the modern deathtouch keyword itself) is a refinement of the same idea, with the trigger moved off the combat step and onto damage so the kill could ride along with non-combat sources: a ping, a fight spell, any sliver of damage at all. That is the real upgrade the combat-step version cannot reach. Reading the card now is reading a design draft: the intent is clear, the execution is constrained by the rules vocabulary available at the time, and the green five-mana 2/4 body is priced for a game that had not yet figured out how to charge for the ability cleanly.