Even if you don't plan on playing, log in daily to get the following rewards:
- 50 A.R.M.O.R. Research Drives
30 Cosmic Worldstones
30 Omega Files
10 Odin Marks
10 Eternity Splinters
10 Cube Shards
and a Legendary Piece of Rainbow
Just the 10 Eternity Splinters would be worth it. I'm not sure how long this event runs but if only 5 days, that could get you almost a 1/3rd of the way to a new hero(175 ES for a random hero unlock), not counting how many you get while playing(average is about 1 per 8 minutes going by some comments in official forums).