Cast as an aura, Eidolon could easily give +5/+5 or greater to the enchanted creature , and it pops out as an equally-sized threat if the enchanted creature loses the battle
Double strike creatures are great blockers since they can take out attackers in the first strike step or trade with them in the regular combat step
I never know when to actually get to a list when Im talking about a deck, so lets get that out of the way: Creatures (31) 4 Elvish Mystic 4 Polukranos, World Eater 1 Nylea, God of the Hunt 4 Sylvan Caryatid 1 Nylea's Disciple 4 Voyaging Satyr 4 Courser of Kruphix 4 Genesis Hydra 4 Whisperwood Elemental 1 Temur Sabertooth Lands (24) Spells (5) Ive gone through several iterations, of course, but this is what Im currently playing on Magic Online
Rebacked cards (like the Alpha Timetwister in the third picture) normally fail this test
Sharkey, Tyrant of the Shire's last ability uses a new template indicating that you may spend mana as though it were mana of any type to activate Sharkey, Tyrant of the Shire's abilities
I love it when a card shows not just the ability, but also the explanation for what that ability means for game play