Viral Quills - spreads AOE viral procs and minor damage
Martyr Symbiosis - sacrifices itself to save you. You can then immediately revive it using Aerial bond + Tenacious Bond (jump and get kills + headshots)
Rank 5 minimum Bite + Tenacious Bond - gives free 1.2x flat crit damage to your weapons
Panzer Devolution - allows you to regenerate every 30s on death, rather than the 60s cooldown for normal pets.
Hunter Recovery - optional mod for healing. Viral quills constantly heals your health while active since it deals damage.
Tek Assault - 60% chance to not die
Fetch - mandatory vacuum
Synth deconstruct - optional for mass producing health orbs, as any enemy touched by Viral Quills has a 25% chance to drop health orb. also gives holster reload bonus.
Primed Animal Instinct is optional since you now get universal radar, but loot radar is still useful

Flex options:
Calculated Redirection + Reinforced Bond over Primed Animal Instinct + Hunter Recovery for bonus 60% fire rate

Tandem bond - good on frames requiring melee combo eg Baruuk, Gara, Khora, Atlas. Viral Quills count as an extra 3 melee combo per spore, meaning Panzer attacking gains up to 18 combo per enemy hit (assuming up to 6 spores). You can reach x12 combo in 10 seconds if you add grouping.

Mystic Bond over primed animal instinct - allows free casts on frames that don't use Brief Respite for shield gating, and Viral Quills helps trigger Mystic Bond

Seismic Bond (gives bonus Ability Efficiency on warframes with CHANNELLING ABILITIES as Viral Quills deals damage. (Eg can be useful on frames with exalted weapons like Mesa, frames with Gloom, Oberon, Ivara etc).