Mirkwood Elk

Six mana is far too slow for most Legacy plans; the narrow return-to-hand trigger is unlikely to justify it over stronger expensive threats such as Koma, World-Eater.

Could be wrong if An established Elf shell with efficient mana or a way to exploit repeated ETBs could make the recursion materially better.

Elf decks can cast it and value an ETB regrowth plus repeated attack triggers, but six mana and a non-Elf body make it a replaceable tribal value card.

Could be wrong if Its standing rises if optimized Elf lists consistently want to rebuy high-impact Elf creatures and can give it haste or repeat ETBs.

A six-mana 6/6 trampler is reliable top-end; returning an Elf on entry makes it a meaningful two-for-one, though revealed Elf density is unknown.

Could be wrong if Low Elf density or a fast environment would leave this as merely an expensive vanilla threat.