Statius needs to invoke the muse to continue his epic, as the poem gets more dark and intense.

Alias nova suggere vires, Calliope, maiorque chelyn mihi tendat Apollo.

Supply new strength, Calliope, and may Apollo string a greater lyre.

Alias: other, new or different

Nova: new

Suggere: supply, in the second person singular present active imperative

Vires: force, strength

Alias, Nova and vires are both feminine plural accusative

Calliope: the muse of epic poetry, and the recipient of the command

Maior: greater; comparative form of magnus meaning great

Que: and

Chelyn: lyre; in the feminine singular accusative 

Mihi: for me; a dative singular pronoun

Tendat: string; in the jussive subjunctive, so expressing a wish

Apollo: nominative singular of the god