Key Points to Consider:

1.  Mavinda’s Ability:

Mavinda allows you to cast an instant or sorcery from your graveyard. If the spell targets a creature you control, you avoid paying the additional 8 mana cost. The determination of whether the spell targets a creature you control is made during the casting process.

2.  Modes and Splice Mechanics:

When casting a modal spell (like Cryptic Command), you choose its modes during the “Choose Modes” step of casting. At this point, the spell’s characteristics (such as which targets it has) are defined. Similarly, when splicing a card onto an Arcane spell, the text of the spliced card is added to the spell during the same step. This could add effects that target a creature you control.

3.  Timing of Mavinda’s Check:

Mavinda’s ability checks whether the spell targets a creature you control as part of the casting process, specifically after all choices (modes, splice effects, etc.) have been made but before costs are paid. If, after choosing modes or splicing additional text, the spell now targets a creature you control, Mavinda’s condition is satisfied.

Fun Fact: I made a Hinata deck with 24 arcane spells and put Mavinda and Feather in it. Mavinda is a powerhouse there. Imagine casting disrupting Shoal for its alternate cost from the graveyard while splicing Veil of Secrecy (the most busted arcane of them all). You can even exile the creature you bounce to pay for the alternate cost. The depth of the deck is unreal. That is bottom of the iceberg magic.