Brass-Talon Chimera

First strike
Sacrifice Brass-Talon Chimera: Put a +2/+2 counter on target Chimera creature. It gains first strike. (This effect lasts indefinitely.)

Toolcraft Exemplar

At the beginning of combat on your turn, if you control an artifact, Toolcraft Exemplar gets +2/+1 until end of turn. If you control three or more artifacts, it also gains first strike until end of turn.

Lead-Belly Chimera

Trample
Sacrifice Lead-Belly Chimera: Put a +2/+2 counter on target Chimera creature. It gains trample. (This effect lasts indefinitely.)

Jhoira's Familiar

Flying
Historic spells you cast cost {1} less to cast. (Artifacts, legendaries, and Sagas are historic.)

Odric, Lunarch Marshal

At the beginning of each combat, creatures you control gain first strike until end of turn if a creature you control has first strike. The same is true for flying, deathtouch, double strike, haste, hexproof, indestructible, lifelink, menace, reach, skulk, trample, and vigilance.

Iron-Heart Chimera

Vigilance
Sacrifice Iron-Heart Chimera: Put a +2/+2 counter on target Chimera creature. It gains vigilance. (This effect lasts indefinitely.)