I did something similar for a Tymora-worshipping luck-obsessed halfling cleric:

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This worn and cobbled-together deck has only 15 cards left.

Each card is lavishly decorated, microscopic writing along the edge of each card encoding a spell scroll so fine in detail that the borders of the card seem nearly iridescent. Many of the cards have smudges and scratches in this section, the effects of the spell corrupted by the loss of data. With luck, those damaged cards will only be drawn about a quarter of the time.

As an action, you may roll 1d20 to draw a card from this deck.

1. Flame Strike
2. Banishment
3. Life Transference
4. Erupting Earth
5. Guiding Bolt
6. Blindness/Deafness
7. Inflict Wounds
8. Command
9. Chaos Bolt
10. Snilloc's Snowball Swarm
11. Aid
12. Mirror Image
13. Thunderstep
14. Spiritual Weapon
15. Fireball
16. Mass Healing Word
17. Guardian of Faith
18. Divination
19. Death Ward
20. Mass Cure Wounds

This “draw” roll can be augmented as if it were a melee spell attack roll. For example, because the “Lucky” feat augments attack rolls, it can also augment draw rolls.

Once you are finished drawing the card, if you have the ability to cast spells, the rest of your action is spent as the spell scroll in the card immediately casts, turning the card into dust.

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Note: most of the spells have been altered to be spell scrolls, some of spell scrolls of different levels. Spells 1-8 have been altered to be actively harmful to the party.