Neo Revelation (2001) included Shining Gyarados and Shining Magikarp, and Neo Destiny (2002) added eight more Shining Pokmon
Possessing the ability to tap to give a target creature +X/+X until end of turn, where X is equal to the number of elves the user controls, Timberwatch Elf can greatly buff up an Elf at any time, allowing for fun mind games
Plus, even the bad mythics (perhaps outside of Apex of Power) aren't really that bad, with the Elder Dragons being worth a couple of bucks (and being relevant for Commander) and Bone Dragon being a sleeper for post-rotation Standard, assuming that Golgari has some sweet graveyard synergies in Guilds of Ravnica
Basing this on Staggershock , I think sounds reasonable
This is often found in low curve decks as a way to recur a recently killed creature often with a powerful enter the battlefield effect such as Chittering Rats or Phyrexian Rager
Yes, mentor does stack