Slinza, the Spiked Stampede

Slinza's second ability applies to all Beasts creatures you control as they enter, even if they wouldn't ordinarily enter with any +1/+1 counters on them.

Slinza's first ability can't reduce the amount of colored mana you pay for a spell. It reduces only the generic mana component of that spell.

If Slinza enters at the same time as one or more other creatures with power 4 or greater, its last ability triggers once for each of those other creatures, plus one more time for itself.

You don't choose a target for Slinza's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you pay {1}{R}{G} this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.