One of the primary methods of acquiring companions is through the gacha; you can either consume five Transient Stones for a random character, or consume fifty for a multi-roll of ten. Multirolls increase the odds of acquiring a higher rarity unit.
Aside from the Main Gacha, event gachas offer modified drop/pull rates (event gachas offer characters with event-relevant skills at a higher drop rate), and sometimes gacha exclusives (Valentine's gacha offered exclusive variants of existing units).
So far, multirolling with all of the character gachas guarantees at least one 
companion. After that, it is safe to assume that rates follow normal single roll rates.
Main Gacha
Co-Op/Friend Gacha
Apprentice Santa's Gift
| Duration | December 23, 2016 @ 17:30 -> January 7, 2017 @ 15:00 |
|---|
New Years
Throughout the week, a gacha was released for one day to offer characters of a specific element (one timed-exclusive new, and others offered at a modified drop rate).
| Duration | January 1st, 2017 -> January 7th, 2017 @ 23:59 |
|---|
Monday: 
FIRE Gacha
Tuesday: 
WATER Gacha
Wednesday: 
WOOD Gacha
Thursday: 
AETHER Gacha
Friday: 
NETHER Gacha
Berserkers Clash
| Original Duration | January 13, 2017 @17:30 -> January 27, 2017 @17:30 |
|---|---|
| Reprint Duration | March 11, 2017 -> March 20, 2017 @23:59 |
Valentine Panic
| Duration | February 10, 2017 @ 17:30 -> February 28, 2017 @ 23:59 |
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Before Spring
| Duration | March 20, 2017 @ 16:00 -> March 31, 2017 @ 23:59 |
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