Hello,
No, these cards are also available as a *rare* drop in Lucky *. This is primarily a big spender event that focuses on RNG, so please keep that in mind when spending/playing.

Here is a brief explanation of how this event works, from Tenkz on the Official Discord

How Nine-Star Treasure Hunt works

There are 9 levels with rewards at levels 3, 6, and 9.

In order to attempt to upgrade the level, you must use an amount of Star Upgrade Cards. On attempting to upgrade you will either upgrade to the next level or you will degrade down by 1 level. You may prevent moving down a level on upgrade failure by doing the attempt with Star Protection Cards.

Note, protects do not guarantee the updgrade, it is still random.

On reaching a level with a reward, you may decide to claim it. If you do, you will reset back to level 1 (cannot protect this).

Upgrade and Protect cards may be purchased in the shop for ingots. Cards may also be randomly dropped (rarely) in Lucky *.

Rewards claim limits:

Silver: unlimited

Gold: 6 times

Diamond: 3 times

Card use per level:

Lvl Upg Pro

1 5 1

2 5 3

3 8 4

4 10 5

5 15 8

6 30 15

7 60 30

8 120 60

Thanks and have a great day!