Bess, Soul Nourisher [Streets of New Capenna Commander]

Whenever one or more other creatures with base power and toughness 1/1 enter the battlefield under your control, put a +1/+1 counter on Bess, Soul Nourisher.
Whenever Bess attacks, each other creature you control with base power and toughness 1/1 gets +X/+X until end of turn, where X is the number of +1/+1 counters on Bess.