Declare Mobile Garrison and Najeela, if able, as attackers.
Mobile Garrison triggers, as well as Najeela if it was declared an attacker.
Resolve the Mobile Garrison trigger, untapping Chromatic Orrery.
Resolve the Najeela trigger, if applicable, creating a 1/1 Warrior creature token that is tapped and attacking.
Holding priority, activate Chromatic Orrery's first ability by tapping it, adding 5.
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 each combat phase.
This loop transforms a simple declaration of attackers into an endless march of combat phases, fueled entirely by the synergy between Najeela, the Blade-Blossom, Mobile Garrison, and Chromatic Orrery. When Mobile Garrison swings, its attack trigger untaps Chromatic Orrery, allowing the Orrery's massive five-mana production to directly fund Najeela's five-color activated ability. Because Chromatic Orrery also lets you spend your mana as though it were any color, the colorless mana generated easily pays for Najeela's precise mana requirements. Every iteration untaps your attackers and grants you another combat phase while Najeela continuously populates the board with tapped and attacking Warrior tokens, letting you steamroll opponents across infinite phases.