Helga, Skittish Seer | Mind Over Matter | Cloudstone Curio

Cards

All permanents on the battlefield.
You have a nonartifact creature card in hand with mana value 4 or greater or with ({X} magic symbol) in its mana cost that can be cast using only one color of mana.
You control a nonartifact creature card with mana value 4 or greater or with ({X} magic symbol) in its mana cost that can be cast using only one color of mana.
Helga does not have summoning sickness.
Helga has a power that is equal to or greater than 4 or the highest mana value among the generic creatures, whichever is greater.

Activate
Helga by tapping it, adding an amount of any one color of mana equal to its power that can only be spent to cast creature spells with mana value 4 or greater or creature spells with ({X} magic symbol) in their mana cost.
Cast the creature with mana value 4 or greater or ({X} magic symbol) in its mana cost by paying its mana cost, ensuring to spend at least four total mana if needed.
Helga triggers, causing you to draw a card, gain 1 life and put a +1/+1 counter on
Helga.
When the creature enters the battlefield,
Cloudstone Curio triggers, returning the other creature with mana value 4 or greater or ({X} magic symbol) in its mana cost from the battlefield to your hand.
Activate
Mind Over Matter by discarding a card, untapping
Helga.
Repeat.

If you have enough leftover mana to cast the creature, you can instead substitute untapping another permanent instead of
Helga.

Infinite self-discard triggers.
Near-infinite lifegain.
Near-infinite lifegain triggers.
Near-infinite ETB.
Infinite draw triggers.
Infinite looting.
Near-infinite storm count.
Near-infinite LTB.
Near-infinite untap of permanents you control.
Near-infinite +1/+1 counters on
Helga.
Near-infinite colored mana that can only be spent to cast creature spells with mana value 4 or greater or creature spells with X in their mana cost.