You may discard a Forest card rather than pay Snag's mana cost.
Prevent all combat damage that would be dealt by unblocked creatures this turn.
Some ideas to help:
Artifacts: If you want people to draw cards, look for Font of Mythos . With many relevant tap abilities, you might want to consider Clock of Omens ? Get extra mileage out of Gilded Lotus , and Howling Mine if you don't want people drawing any more. Also, Darksteel Plate makes the equipped creature difficult to deal with. With all your Fog type effects, have you considered Isochron Scepter ?
Creatures: Some mana ramp creatures possibly? Stuff like Wood Elves , Yavimaya Dryad and Farhaven Elf are all good dudes and work well with your ETB theme. You could also consider Woodfall Primus and Sun Titan to get stuff out of the way and get other things back. Although I'm not sure how many permanents you have with CMC3 or less. There's also Trygon Predator , who's a pretty cool dude. And Restoration Angel for your other ETB effects. Twilight Shepherd is also a good way to recover from Wrath effects. Frost Titan might also be useful here. Keeping problem permanents tapped down.
Enchantments: You might want to consider Faith's Fetters , Prison Term , War Tax , Web of Inertia and Sphere of Safety as other ways of making it awkward for people to attack you. Also, consider Greater Good and Defense of the Heart . Greater Good lets your creatures escape tuck or exile (cough Terminus ), while also potentially drawing you cards.Defense means you can get relevant creatures into play earlier.
Instants: No love for Dawn Charm ? Super useful. Counter that Bonfire of the Damned /Bribery /Diabolic Edict . Save creatures from boardwipes by regenerating them. Or just acting as a plain old Fog . Speaking of Fog, take a look at Moment's Peace . Fog with Flashback. Or Snag for a free Fog if you need it. Also, with all your ETB abilities, Momentary Blink is amazing.
Take a look at Voidslime too. Such a cool and useful card.
Land: If you're going to whole cycling land thing, there's Drifting Meadow , Lonely Sandbar , Remote Isle , Slippery Karst and Blasted Landscape in your colours. To go with these (if you are interested), Life from the Loam makes a pretty nice, if clunky, draw engine.
Seen as you're running Terminus , you might want to consider some sacrifice outlets to "save" the important creatures. High Market is a good one. So is Miren, the Moaning Well . Safe Haven is also another possibility.
Outside of those, other "goodstuff" lands could be useful. Bant Panorama , Reliquary Tower , Command Tower , Eiganjo Castle , Minamo, School at Water's Edge , Homeward Path , Strip Mine and Buried Ruin .
Sorcery: Could possibly consider some tutor type effects? Steelshaper's Gift (and Enlightened Tutor ) both mean you can tutor for relevant stuff like Lightning Greaves or Propaganda for example. Green Sun's Zenith is also god tier, but it's effectiveness is based on how many green creatures you're running.
Think I'm suggested out dude. Take of these what you will. I'm not saying you should run any of them, but they're food for thought hopefully :).