Rock Basilisk

Deathtouch before deathtouch had a keyword. The basilisk ability is one of Magic's oldest design conceits: a creature that kills whatever it touches in combat, the venomous-gaze flavor of myth rendered as a destroy clause that fires at end of combat rather than on damage. What makes this version of the template instructive is how cautiously it is gated. The trigger only cares about blocking or being blocked, so the kill is locked to combat; it does nothing on the stack and nothing to a creature that simply sits back. The Wall exclusion is the other deliberate friction: a sufficiently tough Wall can chump it without being destroyed by the trigger, which means a defensive opponent has a clean answer that a true deathtoucher would shrug off. Six mana for a 4/5 reflects an early-Magic instinct: green and red paid full freight for stats, and the petrifying-stare effect was priced as a premium ability rather than a single keyword tucked onto a two-drop. Modern deathtouch collapsed all of this into one word and stapled it to cheaper bodies, which is precisely why looking back at the basilisk template is worth the trip. It shows the seams of an effect that later design sanded smooth: the timing window and the Wall carve-out spelled out longhand before the rules engine learned to say the same thing in shorthand.