At the beginning of combat on your turn, Halana and Alena triggers, putting at least five +1/+1 counters on Sage of Hours.
Activate Sage of Hours by removing all +1/+1 counters from it, taking at least one extra turn after this one.
Repeat.

Infinite turns

Halana and Alena, Partners

Sage of Hours

Move to combat.
Halana and Alena trigger, putting at least six +1/+1 counters on Crystalline Crawler.
Attack with at least Najeela.
Najeela triggers, creating a 1/1 Warrior creature token that is tapped and attacking.
Activate Crystaline Crawler by removing five +1/+1 counters from it, adding {W}{U}{B}{R}{G}.
Activate Najeela by paying {W}{U}{B}{R}{G}, untapping all attacking creatures, giving them trample, lifelink and haste, and gaining an additional combat phase after this one.
Repeat.

Infinite +1/+1 counters on creatures you control

Infinite colored mana

Infinite combat phases

Infinite creature tokens with haste

Infinite ETB

Infinite lifegain

Infinite lifegain triggers

Najeela, the Blade-Blossom

Crystalline Crawler

Move to combat.
Halana and Alena trigger, putting at least three +1/+1 counters on Cryptic Trilobite.
Attack with at least Najeela.
Najeela triggers, creating a 1/1 Warrior creature token that is tapped and attacking.
Activate Cryptic Trilobite by removing three +1/+1 counters from it, adding {6} that can only be spent to activate abilities.
Activate Najeela by paying {5}, untapping all attacking creatures, giving them trample, lifelink and haste, and gaining an additional combat phase after this one.
Repeat.

Combos with "Halana and Alena, Partners"