Point of fact, this is not how Knuckles died.

He was actually diced into “chunky salsa” by a broken glass golem.

He and Sonic ran off while the party was recovering from a long running battle we had just barely won.  That dungeon was full of these special magical one way doors.  When, separated from the rest of the group, Sonic and Knuckles happened upon one of these doors they, naturally, went through it.  The other side of it opened into a fifteen foot plummet over a pit full of shattered glass shards.  Tasting a little bit of thief blood, the glass rose up, took a vaguely human shape and flayed the two apart.

Technically we never recovered their bodies.

That particular dungeon had a habit of killing characters in ways which reduced them to tiny, unrecognizable pieces.  One of the mages was carrying around a bag into which we just put all of the parts we could recover of the characters who died… the thought being that even though our cleric couldn’t resurrect them, a higher level one might be able to if any of us survived.  By the end, the bag had the cremains of two wizards, little more than DNA samples from a few of the warriors, somebody’s tongue, and two bloody masses which Lisa was convinced were Knuckles’ diced kidneys.